diff --git a/components/codetools/definetemplates.pas b/components/codetools/definetemplates.pas
index d526745ad5..7aadd43690 100644
--- a/components/codetools/definetemplates.pas
+++ b/components/codetools/definetemplates.pas
@@ -231,6 +231,7 @@ type
   public
     Path: string;
     Values: TExpressionEvaluator;
+    UnitLinksTree: TAVLTree;
     constructor Create;
     destructor Destroy; override;
   end;
@@ -269,6 +270,9 @@ type
     procedure IncreaseChangeStep;
   protected
     function FindDirectoryInCache(const Path: string): TDirectoryDefines;
+    function GetDirDefinesForDirectory(const Path: string;
+                                    WithVirtualDir: boolean): TDirectoryDefines;
+    function GetDirDefinesForVirtualDirectory: TDirectoryDefines;
     function MacroFuncExtractFileExt(Data: Pointer): boolean;
     function MacroFuncExtractFilePath(Data: Pointer): boolean;
     function MacroFuncExtractFileName(Data: Pointer): boolean;
@@ -307,6 +311,8 @@ type
     function  GetPPWSrcPathForDirectory(const Directory: string): string;
     function  GetSrcPathForDirectory(const Directory: string): string;
     function  GetUnitPathForDirectory(const Directory: string): string;
+    function  FindUnitInUnitLinks(const AnUnitName, Directory: string;
+                                  WithVirtualDir: boolean): string;
     function  IsEqual(SrcDefineTree: TDefineTree): boolean;
     procedure Add(ADefineTemplate: TDefineTemplate);
     procedure AddChild(ParentTemplate, NewDefineTemplate: TDefineTemplate);
@@ -409,6 +415,7 @@ function DefineActionNameToAction(const s: string): TDefineAction;
 function DefineTemplateFlagsToString(Flags: TDefineTemplateFlags): string;
 function SearchUnitInUnitLinks(const UnitLinks, TheUnitName: string;
   var UnitLinkStart, UnitLinkEnd: integer; var Filename: string): boolean;
+function CreateUnitLinksTree(const UnitLinks: string): TAVLTree;
 function GetDefaultSrcOSForTargetOS(const TargetOS: string): string;
 
 
@@ -452,6 +459,12 @@ begin
   Result:=AnsiCompareText(Link1.UnitName,Link2.UnitName);
 end;
 
+function CompareUnitNameWithUnitLinkNode(UnitName: Pointer;
+  NodeData: pointer): integer;
+begin
+  Result:=AnsiCompareText(String(UnitName),TUnitNameLink(NodeData).UnitName);
+end;
+
 function CompareDirectoryDefines(NodeData1, NodeData2: pointer): integer;
 var DirDef1, DirDef2: TDirectoryDefines;
 begin
@@ -513,6 +526,7 @@ begin
             exit;
           end;
         end;
+        UnitLinkStart:=UnitLinkEnd;
       end else begin
         UnitLinkStart:=UnitLinkEnd+1;
         while (UnitLinkStart<=length(UnitLinks))
@@ -524,6 +538,55 @@ begin
   end;
 end;
 
+function CreateUnitLinksTree(const UnitLinks: string): TAVLTree;
+var
+  UnitLinksTree: TAVLTree;
+  UnitLinkLen: integer;
+  UnitLinkStart: Integer;
+  UnitLinkEnd: Integer;
+  TheUnitName: String;
+  Filename: String;
+  NewNode: TUnitNameLink;
+begin
+  UnitLinksTree:=TAVLTree.Create(@CompareUnitLinkNodes);
+  UnitLinkStart:=1;
+  while UnitLinkStart<=length(UnitLinks) do begin
+    while (UnitLinkStart<=length(UnitLinks))
+    and (UnitLinks[UnitLinkStart] in [#10,#13]) do
+      inc(UnitLinkStart);
+    UnitLinkEnd:=UnitLinkStart;
+    while (UnitLinkEnd<=length(UnitLinks)) and (UnitLinks[UnitLinkEnd]<>' ')
+    do
+      inc(UnitLinkEnd);
+    UnitLinkLen:=UnitLinkEnd-UnitLinkStart;
+    if UnitLinkLen>0 then begin
+      TheUnitName:=copy(UnitLinks,UnitLinkStart,UnitLinkLen);
+      if IsValidIdent(TheUnitName) then begin
+        UnitLinkStart:=UnitLinkEnd+1;
+        UnitLinkEnd:=UnitLinkStart;
+        while (UnitLinkEnd<=length(UnitLinks))
+        and (not (UnitLinks[UnitLinkEnd] in [#10,#13])) do
+          inc(UnitLinkEnd);
+        if UnitLinkEnd>UnitLinkStart then begin
+          Filename:=copy(UnitLinks,UnitLinkStart,UnitLinkEnd-UnitLinkStart);
+          NewNode:=TUnitNameLink.Create;
+          NewNode.UnitName:=TheUnitName;
+          NewNode.Filename:=Filename;
+          UnitLinksTree.Add(NewNode);
+        end;
+        UnitLinkStart:=UnitLinkEnd;
+      end else begin
+        UnitLinkStart:=UnitLinkEnd+1;
+        while (UnitLinkStart<=length(UnitLinks))
+        and (not (UnitLinks[UnitLinkStart] in [#10,#13])) do
+          inc(UnitLinkStart);
+      end;
+    end else
+      break;
+  end;
+  Result:=UnitLinksTree;
+end;
+
 function GetDefaultSrcOSForTargetOS(const TargetOS: string): string;
 begin
   Result:='';
@@ -1496,6 +1559,7 @@ end;
 destructor TDirectoryDefines.Destroy;
 begin
   Values.Free;
+  UnitLinksTree.Free;
   inherited Destroy;
 end;
 
@@ -1610,6 +1674,51 @@ begin
     Result:=nil;
 end;
 
+function TDefineTree.GetDirDefinesForDirectory(const Path: string;
+  WithVirtualDir: boolean): TDirectoryDefines;
+var
+  ExpPath: String;
+begin
+  //writeln('[TDefineTree.GetDirDefinesForDirectory] "',Path,'"');
+  if (Path<>'') or (not WithVirtualDir) then begin
+    ExpPath:=TrimFilename(Path);
+    if (ExpPath<>'') and (ExpPath[length(ExpPath)]<>PathDelim) then
+      ExpPath:=ExpPath+PathDelim;
+    Result:=FindDirectoryInCache(ExpPath);
+    if Result=nil then begin
+      Result:=TDirectoryDefines.Create;
+      Result.Path:=ExpPath;
+      //writeln('[TDefineTree.GetDirDefinesForDirectory] B ',ExpPath,' ');
+      if Calculate(Result) then begin
+        //writeln('[TDefineTree.GetDirDefinesForDirectory] C success');
+        FCache.Add(Result);
+      end else begin
+        //writeln('[TDefineTree.GetDirDefinesForDirectory] D failed');
+        Result.Free;
+        Result:=nil;
+      end;
+    end;
+  end else begin
+    Result:=GetDirDefinesForVirtualDirectory;
+  end;
+end;
+
+function TDefineTree.GetDirDefinesForVirtualDirectory: TDirectoryDefines;
+begin
+  if FVirtualDirCache=nil then begin
+    //writeln('################ TDefineTree.GetDirDefinesForVirtualDirectory');
+    FVirtualDirCache:=TDirectoryDefines.Create;
+    FVirtualDirCache.Path:=VirtualDirectory;
+    if Calculate(FVirtualDirCache) then begin
+      //writeln('TDefineTree.GetDirDefinesForVirtualDirectory ');
+    end else begin
+      FVirtualDirCache.Free;
+      FVirtualDirCache:=nil;
+    end;
+  end;
+  Result:=FVirtualDirCache;
+end;
+
 function TDefineTree.MacroFuncExtractFileExt(Data: Pointer): boolean;
 var
   FuncData: PReadFunctionData;
@@ -1690,6 +1799,32 @@ begin
   end;
 end;
 
+function TDefineTree.FindUnitInUnitLinks(const AnUnitName, Directory: string;
+  WithVirtualDir: boolean): string;
+var
+  DirDef: TDirectoryDefines;
+  UnitLinks: string;
+  AVLNode: TAVLTreeNode;
+begin
+  Result:='';
+  if AnUnitName='' then exit;
+  DirDef:=GetDirDefinesForDirectory(Directory,WithVirtualDir);
+  if (DirDef=nil) or (DirDef.Values=nil) then exit;
+  if DirDef.UnitLinksTree=nil then begin
+    // create tree
+    UnitLinks:=DirDef.Values[ExternalMacroStart+'UnitLinks'];
+    // cache tree
+    DirDef.UnitLinksTree:=CreateUnitLinksTree(UnitLinks);
+  end;
+  // search in tree
+  if DirDef.UnitLinksTree<>nil then begin
+    AVLNode:=DirDef.UnitLinksTree.FindKey(PChar(AnUnitName),
+                                              @CompareUnitNameWithUnitLinkNode);
+    if AVLNode<>nil then
+      Result:=TUnitNameLink(AVLNode.Data).Filename;
+  end;
+end;
+
 function TDefineTree.GetIncludePathForDirectory(const Directory: string
   ): string;
 var Evaluator: TExpressionEvaluator;
@@ -1764,53 +1899,25 @@ end;
 
 function TDefineTree.GetDefinesForDirectory(
   const Path: string; WithVirtualDir: boolean): TExpressionEvaluator;
-var ExpPath: string;
+var
   DirDef: TDirectoryDefines;
 begin
-  //writeln('[TDefineTree.GetDefinesForDirectory] "',Path,'"');
-  if (Path<>'') or (not WithVirtualDir) then begin
-    ExpPath:=TrimFilename(Path);
-    if (ExpPath<>'') and (ExpPath[length(ExpPath)]<>PathDelim) then
-      ExpPath:=ExpPath+PathDelim;
-    DirDef:=FindDirectoryInCache(ExpPath);
-    if DirDef<>nil then begin
-      Result:=DirDef.Values;
-    end else begin
-      DirDef:=TDirectoryDefines.Create;
-      DirDef.Path:=ExpPath;
-      //writeln('[TDefineTree.GetDefinesForDirectory] B ',ExpPath,' ');
-      if Calculate(DirDef) then begin
-        //writeln('[TDefineTree.GetDefinesForDirectory] C success');
-        FCache.Add(DirDef);
-        Result:=DirDef.Values;
-      end else begin
-        //writeln('[TDefineTree.GetDefinesForDirectory] D failed');
-        DirDef.Free;
-        Result:=nil;
-      end;
-    end;
-  end else begin
-    Result:=GetDefinesForVirtualDirectory;
-  end;
+  DirDef:=GetDirDefinesForDirectory(Path,WithVirtualDir);
+  if DirDef<>nil then
+    Result:=DirDef.Values
+  else
+    Result:=nil;
 end;
 
 function TDefineTree.GetDefinesForVirtualDirectory: TExpressionEvaluator;
+var
+  DirDef: TDirectoryDefines;
 begin
-  if FVirtualDirCache<>nil then
-    Result:=FVirtualDirCache.Values
-  else begin
-    //writeln('################ TDefineTree.GetDefinesForVirtualDirectory');
-    FVirtualDirCache:=TDirectoryDefines.Create;
-    FVirtualDirCache.Path:=VirtualDirectory;
-    if Calculate(FVirtualDirCache) then begin
-      Result:=FVirtualDirCache.Values;
-      //writeln('TDefineTree.GetDefinesForVirtualDirectory ',Result.AsString);
-    end else begin
-      FVirtualDirCache.Free;
-      FVirtualDirCache:=nil;
-      Result:=nil;
-    end;
-  end;
+  DirDef:=GetDirDefinesForVirtualDirectory;
+  if DirDef<>nil then
+    Result:=DirDef.Values
+  else
+    Result:=nil;
 end;
 
 procedure TDefineTree.ReadValue(const DirDef: TDirectoryDefines;
diff --git a/ide/lazarusidestrconsts.pas b/ide/lazarusidestrconsts.pas
index 1372fdd21b..04ae310d71 100644
--- a/ide/lazarusidestrconsts.pas
+++ b/ide/lazarusidestrconsts.pas
@@ -1827,6 +1827,18 @@ resourcestring
   lisPkgMangCircleInPackageDependencies = 'Circle in package dependencies';
   lisPkgMangThereIsACircleInTheRequiredPackages = 'There is a circle in the '
     +'required packages. See package graph.';
+  lisPkgMangThereAreTwoUnitsWithTheSameName1From2From = 'There are two units '
+    +'with the same name:%s%s1. %s%s%s from %s%s2. %s%s%s from %s%s%s';
+  lisPkgMangThereIsAUnitWithTheSameNameAsAPackage1From2 = 'There is a unit '
+    +'with the same name as a package:%s%s1. %s%s%s from %s%s2. %s%s%s%s';
+  lisPkgMangAmbigiousUnitsFound = 'Ambigious units found';
+  lisPkgMangBothPackagesAreConnectedThisMeansEitherOnePackageU = '%sBoth '
+    +'packages are connected. This means, either one package uses the other, '
+    +'or they are both used by a third package.';
+  lisPkgMangThereIsAFPCUnitWithTheSameNameFrom = 'There is a FPC unit with '
+    +'the same name:%s%s%s%s%s from %s%s%s';
+  lisPkgMangThereIsAFPCUnitWithTheSameNameAsAPackage = 'There is a FPC unit '
+    +'with the same name as a package:%s%s%s%s%s%s';
   lisPkgMangErrorWritingFile = 'Error writing file';
   lisPkgMangUnableToWriteStateFileOfPackageError = 'Unable to write state '
     +'file %s%s%s%sof package %s.%sError: %s';
diff --git a/languages/lazaruside.ca.po b/languages/lazaruside.ca.po
index f5df16bc4c..7aa12b1279 100644
--- a/languages/lazaruside.ca.po
+++ b/languages/lazaruside.ca.po
@@ -94,6 +94,10 @@ msgstr "%s, espec
 msgid "%s/ReadOnly"
 msgstr "%s/Només de lectura"
 
+#: lazarusidestrconsts:lispkgmangbothpackagesareconnectedthismeanseitheronepackageu
+msgid "%sBoth packages are connected. This means, either one package uses the other, or they are both used by a third package."
+msgstr ""
+
 #: lazarusidestrconsts:lisoipdescriptiondescription
 msgid "%sDescription:  %s"
 msgstr ""
@@ -414,6 +418,10 @@ msgstr ""
 msgid "Ambigious Unit Name"
 msgstr ""
 
+#: lazarusidestrconsts:lispkgmangambigiousunitsfound
+msgid "Ambigious units found"
+msgstr ""
+
 #: lazarusidestrconsts:lisa2pancestortype
 msgid "Ancestor Type"
 msgstr ""
@@ -5610,6 +5618,10 @@ msgstr ""
 msgid "There are other files in the directory with the same name,%swhich only differ in case:%s%s%sDelete them?"
 msgstr ""
 
+#: lazarusidestrconsts:lispkgmangtherearetwounitswiththesamename1from2from
+msgid "There are two units with the same name:%s%s1. %s%s%s from %s%s2. %s%s%s from %s%s%s"
+msgstr ""
+
 #: lazarusidestrconsts:lispkgmangthereisacircleintherequiredpackages
 msgid "There is a circle in the required packages. See package graph."
 msgstr ""
@@ -5618,6 +5630,14 @@ msgstr ""
 msgid "There is a file with the same name and a similar extension ond disk%sFile: %s%sAmbigious File: %s%s%sDelete ambigious file?"
 msgstr ""
 
+#: lazarusidestrconsts:lispkgmangthereisafpcunitwiththesamenameasapackage
+msgid "There is a FPC unit with the same name as a package:%s%s%s%s%s%s"
+msgstr ""
+
+#: lazarusidestrconsts:lispkgmangthereisafpcunitwiththesamenamefrom
+msgid "There is a FPC unit with the same name:%s%s%s%s%s from %s%s%s"
+msgstr ""
+
 #: lazarusidestrconsts:lisexttoolthereisamaximumoftools
 msgid "There is a maximum of %s tools."
 msgstr ""
@@ -5626,6 +5646,10 @@ msgstr ""
 msgid "There is a unit with the name %s%s%s in the project.%sPlz choose a different name"
 msgstr ""
 
+#: lazarusidestrconsts:lispkgmangthereisaunitwiththesamenameasapackage1from2
+msgid "There is a unit with the same name as a package:%s%s1. %s%s%s from %s%s2. %s%s%s%s"
+msgstr ""
+
 #: lazarusidestrconsts:listhereisalreadyaformwiththename
 msgid "There is already a form with the name %s%s%s"
 msgstr ""
diff --git a/languages/lazaruside.de.po b/languages/lazaruside.de.po
index 9040042b18..128dc1d2fc 100644
--- a/languages/lazaruside.de.po
+++ b/languages/lazaruside.de.po
@@ -104,6 +104,10 @@ msgstr "%s, Projekt spezifisch"
 msgid "%s/ReadOnly"
 msgstr "%s/Nur Lesbar"
 
+#: lazarusidestrconsts:lispkgmangbothpackagesareconnectedthismeanseitheronepackageu
+msgid "%sBoth packages are connected. This means, either one package uses the other, or they are both used by a third package."
+msgstr ""
+
 #: lazarusidestrconsts:lisoipdescriptiondescription
 msgid "%sDescription:  %s"
 msgstr "%sBeschreibung:  %s"
@@ -424,6 +428,10 @@ msgstr ""
 msgid "Ambigious Unit Name"
 msgstr ""
 
+#: lazarusidestrconsts:lispkgmangambigiousunitsfound
+msgid "Ambigious units found"
+msgstr ""
+
 #: lazarusidestrconsts:lisa2pancestortype
 msgid "Ancestor Type"
 msgstr ""
@@ -5620,6 +5628,10 @@ msgstr ""
 msgid "There are other files in the directory with the same name,%swhich only differ in case:%s%s%sDelete them?"
 msgstr ""
 
+#: lazarusidestrconsts:lispkgmangtherearetwounitswiththesamename1from2from
+msgid "There are two units with the same name:%s%s1. %s%s%s from %s%s2. %s%s%s from %s%s%s"
+msgstr ""
+
 #: lazarusidestrconsts:lispkgmangthereisacircleintherequiredpackages
 msgid "There is a circle in the required packages. See package graph."
 msgstr ""
@@ -5628,6 +5640,14 @@ msgstr ""
 msgid "There is a file with the same name and a similar extension ond disk%sFile: %s%sAmbigious File: %s%s%sDelete ambigious file?"
 msgstr ""
 
+#: lazarusidestrconsts:lispkgmangthereisafpcunitwiththesamenameasapackage
+msgid "There is a FPC unit with the same name as a package:%s%s%s%s%s%s"
+msgstr ""
+
+#: lazarusidestrconsts:lispkgmangthereisafpcunitwiththesamenamefrom
+msgid "There is a FPC unit with the same name:%s%s%s%s%s from %s%s%s"
+msgstr ""
+
 #: lazarusidestrconsts:lisexttoolthereisamaximumoftools
 msgid "There is a maximum of %s tools."
 msgstr ""
@@ -5636,6 +5656,10 @@ msgstr ""
 msgid "There is a unit with the name %s%s%s in the project.%sPlz choose a different name"
 msgstr ""
 
+#: lazarusidestrconsts:lispkgmangthereisaunitwiththesamenameasapackage1from2
+msgid "There is a unit with the same name as a package:%s%s1. %s%s%s from %s%s2. %s%s%s%s"
+msgstr ""
+
 #: lazarusidestrconsts:listhereisalreadyaformwiththename
 msgid "There is already a form with the name %s%s%s"
 msgstr ""
diff --git a/languages/lazaruside.es.po b/languages/lazaruside.es.po
index 296772703e..82e39e09b8 100644
--- a/languages/lazaruside.es.po
+++ b/languages/lazaruside.es.po
@@ -105,6 +105,10 @@ msgstr "%s, específico de proyecto"
 msgid "%s/ReadOnly"
 msgstr "%s/Sólo de lectura"
 
+#: lazarusidestrconsts:lispkgmangbothpackagesareconnectedthismeanseitheronepackageu
+msgid "%sBoth packages are connected. This means, either one package uses the other, or they are both used by a third package."
+msgstr ""
+
 #: lazarusidestrconsts:lisoipdescriptiondescription
 msgid "%sDescription:  %s"
 msgstr "%s Descripción: %s"
@@ -425,6 +429,10 @@ msgstr "Encontrados archivos ambiguos"
 msgid "Ambigious Unit Name"
 msgstr "Nombre de Unidad ambiguo"
 
+#: lazarusidestrconsts:lispkgmangambigiousunitsfound
+msgid "Ambigious units found"
+msgstr ""
+
 #: lazarusidestrconsts:lisa2pancestortype
 msgid "Ancestor Type"
 msgstr "Tipo del ancestro"
@@ -5621,6 +5629,10 @@ msgstr "Hay másfunciones en el menú contextual"
 msgid "There are other files in the directory with the same name,%swhich only differ in case:%s%s%sDelete them?"
 msgstr "Hay otros archivos en el directorio con el mismo nombre,%s difieren sólo en may/min:%s%s%s¿Borrarlos?"
 
+#: lazarusidestrconsts:lispkgmangtherearetwounitswiththesamename1from2from
+msgid "There are two units with the same name:%s%s1. %s%s%s from %s%s2. %s%s%s from %s%s%s"
+msgstr ""
+
 #: lazarusidestrconsts:lispkgmangthereisacircleintherequiredpackages
 msgid "There is a circle in the required packages. See package graph."
 msgstr "Hay un círculo en los paquetes requeridos. Mire el gráfico de paquete"
@@ -5629,6 +5641,14 @@ msgstr "Hay un círculo en los paquetes requeridos. Mire el gráfico de paquete"
 msgid "There is a file with the same name and a similar extension ond disk%sFile: %s%sAmbigious File: %s%s%sDelete ambigious file?"
 msgstr "Hay un archivo con el mismo nombre y extensión similar en disco%sArchivo: %s%sArchivo Ambiguo: %s%s%s¿Borrar archivo ambiguo?"
 
+#: lazarusidestrconsts:lispkgmangthereisafpcunitwiththesamenameasapackage
+msgid "There is a FPC unit with the same name as a package:%s%s%s%s%s%s"
+msgstr ""
+
+#: lazarusidestrconsts:lispkgmangthereisafpcunitwiththesamenamefrom
+msgid "There is a FPC unit with the same name:%s%s%s%s%s from %s%s%s"
+msgstr ""
+
 #: lazarusidestrconsts:lisexttoolthereisamaximumoftools
 msgid "There is a maximum of %s tools."
 msgstr "Hay un máximo de %s herramientas"
@@ -5637,6 +5657,10 @@ msgstr "Hay un máximo de %s herramientas"
 msgid "There is a unit with the name %s%s%s in the project.%sPlz choose a different name"
 msgstr "Hay una unidad con el nombre %s%s%s en el proyecto.%sPor favor escoja un nombre diferente"
 
+#: lazarusidestrconsts:lispkgmangthereisaunitwiththesamenameasapackage1from2
+msgid "There is a unit with the same name as a package:%s%s1. %s%s%s from %s%s2. %s%s%s%s"
+msgstr ""
+
 #: lazarusidestrconsts:listhereisalreadyaformwiththename
 msgid "There is already a form with the name %s%s%s"
 msgstr "Ya hay un formulario con el nombre %s%s%s"
diff --git a/languages/lazaruside.fr.po b/languages/lazaruside.fr.po
index 7762e7ea7f..c75ec5d5be 100644
--- a/languages/lazaruside.fr.po
+++ b/languages/lazaruside.fr.po
@@ -103,6 +103,10 @@ msgstr "%s, projet sp
 msgid "%s/ReadOnly"
 msgstr "%s/Lecture seule"
 
+#: lazarusidestrconsts:lispkgmangbothpackagesareconnectedthismeanseitheronepackageu
+msgid "%sBoth packages are connected. This means, either one package uses the other, or they are both used by a third package."
+msgstr ""
+
 #: lazarusidestrconsts:lisoipdescriptiondescription
 msgid "%sDescription:  %s"
 msgstr "%sDescription: %s"
@@ -423,6 +427,10 @@ msgstr "Ambigu
 msgid "Ambigious Unit Name"
 msgstr "Ambiguïté de nom d'unité"
 
+#: lazarusidestrconsts:lispkgmangambigiousunitsfound
+msgid "Ambigious units found"
+msgstr ""
+
 #: lazarusidestrconsts:lisa2pancestortype
 msgid "Ancestor Type"
 msgstr "Type d'ancètre"
@@ -5619,6 +5627,10 @@ msgstr ""
 msgid "There are other files in the directory with the same name,%swhich only differ in case:%s%s%sDelete them?"
 msgstr ""
 
+#: lazarusidestrconsts:lispkgmangtherearetwounitswiththesamename1from2from
+msgid "There are two units with the same name:%s%s1. %s%s%s from %s%s2. %s%s%s from %s%s%s"
+msgstr ""
+
 #: lazarusidestrconsts:lispkgmangthereisacircleintherequiredpackages
 msgid "There is a circle in the required packages. See package graph."
 msgstr ""
@@ -5627,6 +5639,14 @@ msgstr ""
 msgid "There is a file with the same name and a similar extension ond disk%sFile: %s%sAmbigious File: %s%s%sDelete ambigious file?"
 msgstr ""
 
+#: lazarusidestrconsts:lispkgmangthereisafpcunitwiththesamenameasapackage
+msgid "There is a FPC unit with the same name as a package:%s%s%s%s%s%s"
+msgstr ""
+
+#: lazarusidestrconsts:lispkgmangthereisafpcunitwiththesamenamefrom
+msgid "There is a FPC unit with the same name:%s%s%s%s%s from %s%s%s"
+msgstr ""
+
 #: lazarusidestrconsts:lisexttoolthereisamaximumoftools
 msgid "There is a maximum of %s tools."
 msgstr ""
@@ -5635,6 +5655,10 @@ msgstr ""
 msgid "There is a unit with the name %s%s%s in the project.%sPlz choose a different name"
 msgstr ""
 
+#: lazarusidestrconsts:lispkgmangthereisaunitwiththesamenameasapackage1from2
+msgid "There is a unit with the same name as a package:%s%s1. %s%s%s from %s%s2. %s%s%s%s"
+msgstr ""
+
 #: lazarusidestrconsts:listhereisalreadyaformwiththename
 msgid "There is already a form with the name %s%s%s"
 msgstr ""
diff --git a/languages/lazaruside.it.po b/languages/lazaruside.it.po
index d7186529cd..c7ac828517 100644
--- a/languages/lazaruside.it.po
+++ b/languages/lazaruside.it.po
@@ -103,6 +103,10 @@ msgstr "%s, specifica del progetto"
 msgid "%s/ReadOnly"
 msgstr "%s/SolaLettura"
 
+#: lazarusidestrconsts:lispkgmangbothpackagesareconnectedthismeanseitheronepackageu
+msgid "%sBoth packages are connected. This means, either one package uses the other, or they are both used by a third package."
+msgstr ""
+
 #: lazarusidestrconsts:lisoipdescriptiondescription
 msgid "%sDescription:  %s"
 msgstr "%sDescrizione:  %s"
@@ -423,6 +427,10 @@ msgstr "Trovati file ambigui"
 msgid "Ambigious Unit Name"
 msgstr "Nome unit ambiguo"
 
+#: lazarusidestrconsts:lispkgmangambigiousunitsfound
+msgid "Ambigious units found"
+msgstr ""
+
 #: lazarusidestrconsts:lisa2pancestortype
 msgid "Ancestor Type"
 msgstr "Tipo antenato"
@@ -5619,6 +5627,10 @@ msgstr "Ci sono più funzioni nel menu a scomparsa"
 msgid "There are other files in the directory with the same name,%swhich only differ in case:%s%s%sDelete them?"
 msgstr "Ci sono altri file nella directory con lo stesso nome,%sche differiscono solamente per le maiuscole:%s%s%sVuoi cancellarli?"
 
+#: lazarusidestrconsts:lispkgmangtherearetwounitswiththesamename1from2from
+msgid "There are two units with the same name:%s%s1. %s%s%s from %s%s2. %s%s%s from %s%s%s"
+msgstr ""
+
 #: lazarusidestrconsts:lispkgmangthereisacircleintherequiredpackages
 msgid "There is a circle in the required packages. See package graph."
 msgstr "C'è un riferimento circolare nel pacchetto richiesto. Vedere il grafico pacchetto."
@@ -5627,6 +5639,14 @@ msgstr "C'è un riferimento circolare nel pacchetto richiesto. Vedere il grafico
 msgid "There is a file with the same name and a similar extension ond disk%sFile: %s%sAmbigious File: %s%s%sDelete ambigious file?"
 msgstr "C'è un file con lo stesso nome e un'estensione simile su disco%sFile: %s%sFile ambiguo: %s%s%sCancellare il file ambiguo?"
 
+#: lazarusidestrconsts:lispkgmangthereisafpcunitwiththesamenameasapackage
+msgid "There is a FPC unit with the same name as a package:%s%s%s%s%s%s"
+msgstr ""
+
+#: lazarusidestrconsts:lispkgmangthereisafpcunitwiththesamenamefrom
+msgid "There is a FPC unit with the same name:%s%s%s%s%s from %s%s%s"
+msgstr ""
+
 #: lazarusidestrconsts:lisexttoolthereisamaximumoftools
 msgid "There is a maximum of %s tools."
 msgstr "C'è un massimo di %s strumenti."
@@ -5635,6 +5655,10 @@ msgstr "C'è un massimo di %s strumenti."
 msgid "There is a unit with the name %s%s%s in the project.%sPlz choose a different name"
 msgstr "C'è già una unit con nome %s%s%s nel progetto.%sScegliere un altro nome."
 
+#: lazarusidestrconsts:lispkgmangthereisaunitwiththesamenameasapackage1from2
+msgid "There is a unit with the same name as a package:%s%s1. %s%s%s from %s%s2. %s%s%s%s"
+msgstr ""
+
 #: lazarusidestrconsts:listhereisalreadyaformwiththename
 msgid "There is already a form with the name %s%s%s"
 msgstr "C'è già una form con il nome %s%s%s"
diff --git a/languages/lazaruside.pl.po b/languages/lazaruside.pl.po
index 1c1d98bdfe..6de0bf7c48 100644
--- a/languages/lazaruside.pl.po
+++ b/languages/lazaruside.pl.po
@@ -104,6 +104,10 @@ msgstr "%s, szczeg
 msgid "%s/ReadOnly"
 msgstr "%s/Tylko do odczytu"
 
+#: lazarusidestrconsts:lispkgmangbothpackagesareconnectedthismeanseitheronepackageu
+msgid "%sBoth packages are connected. This means, either one package uses the other, or they are both used by a third package."
+msgstr ""
+
 #: lazarusidestrconsts:lisoipdescriptiondescription
 msgid "%sDescription:  %s"
 msgstr "%sOpis:  %s"
@@ -424,6 +428,10 @@ msgstr "Znalaz
 msgid "Ambigious Unit Name"
 msgstr "Niejednoznaczna nazwa modu³u"
 
+#: lazarusidestrconsts:lispkgmangambigiousunitsfound
+msgid "Ambigious units found"
+msgstr ""
+
 #: lazarusidestrconsts:lisa2pancestortype
 msgid "Ancestor Type"
 msgstr "Typ przodka"
@@ -5620,6 +5628,10 @@ msgstr "Wi
 msgid "There are other files in the directory with the same name,%swhich only differ in case:%s%s%sDelete them?"
 msgstr "W katalogu s± inne pliki o tej nazwie,%sktóre ró¿ni± siê tylko wielko¶ci± liter:%s%s%sChcesz je usun±æ?"
 
+#: lazarusidestrconsts:lispkgmangtherearetwounitswiththesamename1from2from
+msgid "There are two units with the same name:%s%s1. %s%s%s from %s%s2. %s%s%s from %s%s%s"
+msgstr ""
+
 #: lazarusidestrconsts:lispkgmangthereisacircleintherequiredpackages
 msgid "There is a circle in the required packages. See package graph."
 msgstr "Wyst±pi³o zapêtlenie zale¿no¶ci w wymaganych pakietach. Spójrz na listê pakietów."
@@ -5628,6 +5640,14 @@ msgstr "Wyst
 msgid "There is a file with the same name and a similar extension ond disk%sFile: %s%sAmbigious File: %s%s%sDelete ambigious file?"
 msgstr "Istnieje plik z tak± sam± nazw± i podobnym rozszerzeniem na dysku%sPlik: %s%sNiejednoznaczny plik: %s%s%sUsun±æ niejednoznaczny plik?"
 
+#: lazarusidestrconsts:lispkgmangthereisafpcunitwiththesamenameasapackage
+msgid "There is a FPC unit with the same name as a package:%s%s%s%s%s%s"
+msgstr ""
+
+#: lazarusidestrconsts:lispkgmangthereisafpcunitwiththesamenamefrom
+msgid "There is a FPC unit with the same name:%s%s%s%s%s from %s%s%s"
+msgstr ""
+
 #: lazarusidestrconsts:lisexttoolthereisamaximumoftools
 msgid "There is a maximum of %s tools."
 msgstr "Mo¿e byæ maksymalnie %s narzêdzi."
@@ -5636,6 +5656,10 @@ msgstr "Mo
 msgid "There is a unit with the name %s%s%s in the project.%sPlz choose a different name"
 msgstr "Modu³ o nazwie %s%s%s jest ju¿ w projekcie.%sWybierz inn± nazwê."
 
+#: lazarusidestrconsts:lispkgmangthereisaunitwiththesamenameasapackage1from2
+msgid "There is a unit with the same name as a package:%s%s1. %s%s%s from %s%s2. %s%s%s%s"
+msgstr ""
+
 #: lazarusidestrconsts:listhereisalreadyaformwiththename
 msgid "There is already a form with the name %s%s%s"
 msgstr "Ju¿ jest formularz o nazwie %s%s%s"
diff --git a/languages/lazaruside.po b/languages/lazaruside.po
index a193d4b313..06c444ed40 100644
--- a/languages/lazaruside.po
+++ b/languages/lazaruside.po
@@ -5594,6 +5594,30 @@ msgstr ""
 msgid "There is a circle in the required packages. See package graph."
 msgstr ""
 
+#: lazarusidestrconsts:lispkgmangtherearetwounitswiththesamename1from2from
+msgid "There are two units with the same name:%s%s1. %s%s%s from %s%s2. %s%s%s from %s%s%s"
+msgstr ""
+
+#: lazarusidestrconsts:lispkgmangthereisaunitwiththesamenameasapackage1from2
+msgid "There is a unit with the same name as a package:%s%s1. %s%s%s from %s%s2. %s%s%s%s"
+msgstr ""
+
+#: lazarusidestrconsts:lispkgmangambigiousunitsfound
+msgid "Ambigious units found"
+msgstr ""
+
+#: lazarusidestrconsts:lispkgmangbothpackagesareconnectedthismeanseitheronepackageu
+msgid "%sBoth packages are connected. This means, either one package uses the other, or they are both used by a third package."
+msgstr ""
+
+#: lazarusidestrconsts:lispkgmangthereisafpcunitwiththesamenamefrom
+msgid "There is a FPC unit with the same name:%s%s%s%s%s from %s%s%s"
+msgstr ""
+
+#: lazarusidestrconsts:lispkgmangthereisafpcunitwiththesamenameasapackage
+msgid "There is a FPC unit with the same name as a package:%s%s%s%s%s%s"
+msgstr ""
+
 #: lazarusidestrconsts:lispkgmangerrorwritingfile
 msgid "Error writing file"
 msgstr ""
diff --git a/languages/lazaruside.ru.po b/languages/lazaruside.ru.po
index 6bae1f1431..03bff4a824 100644
--- a/languages/lazaruside.ru.po
+++ b/languages/lazaruside.ru.po
@@ -94,6 +94,10 @@ msgstr "%s, 
 msgid "%s/ReadOnly"
 msgstr "%s/ÔÏÌØËÏ ÞÔÅÎÉÅ"
 
+#: lazarusidestrconsts:lispkgmangbothpackagesareconnectedthismeanseitheronepackageu
+msgid "%sBoth packages are connected. This means, either one package uses the other, or they are both used by a third package."
+msgstr ""
+
 #: lazarusidestrconsts:lisoipdescriptiondescription
 msgid "%sDescription:  %s"
 msgstr "%sïÐÉÓÁÎÉÅ: %s"
@@ -414,6 +418,10 @@ msgstr "
 msgid "Ambigious Unit Name"
 msgstr "ä×ÕÓÍÙÓÌÅÎÎÏÅ ÉÍÑ ÍÏÄÕÌÑ"
 
+#: lazarusidestrconsts:lispkgmangambigiousunitsfound
+msgid "Ambigious units found"
+msgstr ""
+
 #: lazarusidestrconsts:lisa2pancestortype
 msgid "Ancestor Type"
 msgstr "ôÉÐ ÐÒÅÄËÁ"
@@ -5610,6 +5618,10 @@ msgstr "
 msgid "There are other files in the directory with the same name,%swhich only differ in case:%s%s%sDelete them?"
 msgstr "÷ ËÁÔÁÌÏÇÅ ÅÓÔØ É ÄÒÕÇÉÅ ÆÁÊÌÙ Ó ÔÁËÉÍ ÖÅ ÉÍÅÎÅÍ,%sÏÔÌÉÞÁÀÝÉÅÓÑ ÔÏÌØËÏ ÒÅÇÉÓÔÒÏÍ:%s%s%sõÄÁÌÉÔØ ÉÈ?"
 
+#: lazarusidestrconsts:lispkgmangtherearetwounitswiththesamename1from2from
+msgid "There are two units with the same name:%s%s1. %s%s%s from %s%s2. %s%s%s from %s%s%s"
+msgstr ""
+
 #: lazarusidestrconsts:lispkgmangthereisacircleintherequiredpackages
 msgid "There is a circle in the required packages. See package graph."
 msgstr "ïÂÎÁÒÕÖÅÎ ÃÉËÌ ÚÁ×ÉÓÉÍÏÓÔÅÊ ÐÁËÅÔÏ×. óÍÏÔÒÉÔÅ ÄÉÁÇÒÁÍÍÕ ÐÁËÅÔÏ×."
@@ -5618,6 +5630,14 @@ msgstr "
 msgid "There is a file with the same name and a similar extension ond disk%sFile: %s%sAmbigious File: %s%s%sDelete ambigious file?"
 msgstr "îÁ ÄÉÓËÅ ÅÓÔØ ÆÁÊÌ Ó ÔÁËÉÍ ÖÅ ÉÍÅÎÅÍ É ÐÏÈÏÖÉÍ ÒÁÓÛÉÒÅÎÉÅÍ%sæÁÊÌ: %s%sðÏÈÏÖÉÊ ÆÁÊÌ: %s%s%sõÄÁÌÉÔØ ×ÔÏÒÏÊ ÆÁÊÌ?"
 
+#: lazarusidestrconsts:lispkgmangthereisafpcunitwiththesamenameasapackage
+msgid "There is a FPC unit with the same name as a package:%s%s%s%s%s%s"
+msgstr ""
+
+#: lazarusidestrconsts:lispkgmangthereisafpcunitwiththesamenamefrom
+msgid "There is a FPC unit with the same name:%s%s%s%s%s from %s%s%s"
+msgstr ""
+
 #: lazarusidestrconsts:lisexttoolthereisamaximumoftools
 msgid "There is a maximum of %s tools."
 msgstr "äÏÐÕÓËÁÅÔÓÑ ÍÁËÓÉÍÕÍ %s ÉÎÓÔÒÕÍÅÎÔÏ×."
@@ -5626,6 +5646,10 @@ msgstr "
 msgid "There is a unit with the name %s%s%s in the project.%sPlz choose a different name"
 msgstr "÷ ÐÒÏÅËÔÅ ÅÓÔØ ÍÏÄÕÌØ Ó ÉÍÅÎÅÍ %s%s%s.%s÷ÙÂÅÒÉÔÅ ÄÒÕÇÏÅ ÉÍÑ"
 
+#: lazarusidestrconsts:lispkgmangthereisaunitwiththesamenameasapackage1from2
+msgid "There is a unit with the same name as a package:%s%s1. %s%s%s from %s%s2. %s%s%s%s"
+msgstr ""
+
 #: lazarusidestrconsts:listhereisalreadyaformwiththename
 msgid "There is already a form with the name %s%s%s"
 msgstr "õÖÅ ÅÓÔØ ÆÏÒÍÁ Ó ÉÍÅÎÅÍ %s%s%s"
diff --git a/languages/lazaruside.ruwin.po b/languages/lazaruside.ruwin.po
index f2fb547b62..c03c46fee4 100644
--- a/languages/lazaruside.ruwin.po
+++ b/languages/lazaruside.ruwin.po
@@ -94,6 +94,10 @@ msgstr "%s, 
 msgid "%s/ReadOnly"
 msgstr "%s/òîëüêî ÷òåíèå"
 
+#: lazarusidestrconsts:lispkgmangbothpackagesareconnectedthismeanseitheronepackageu
+msgid "%sBoth packages are connected. This means, either one package uses the other, or they are both used by a third package."
+msgstr ""
+
 #: lazarusidestrconsts:lisoipdescriptiondescription
 msgid "%sDescription:  %s"
 msgstr "%sÎïèñàíèå: %s"
@@ -414,6 +418,10 @@ msgstr "
 msgid "Ambigious Unit Name"
 msgstr "Äâóñìûñëåííîå èìÿ ìîäóëÿ"
 
+#: lazarusidestrconsts:lispkgmangambigiousunitsfound
+msgid "Ambigious units found"
+msgstr ""
+
 #: lazarusidestrconsts:lisa2pancestortype
 msgid "Ancestor Type"
 msgstr "Òèï ïðåäêà"
@@ -5610,6 +5618,10 @@ msgstr "
 msgid "There are other files in the directory with the same name,%swhich only differ in case:%s%s%sDelete them?"
 msgstr " êàòàëîãå åñòü è äðóãèå ôàéëû ñ òàêèì æå èìåíåì,%sîòëè÷àþùèåñÿ òîëüêî ðåãèñòðîì:%s%s%sÓäàëèòü èõ?"
 
+#: lazarusidestrconsts:lispkgmangtherearetwounitswiththesamename1from2from
+msgid "There are two units with the same name:%s%s1. %s%s%s from %s%s2. %s%s%s from %s%s%s"
+msgstr ""
+
 #: lazarusidestrconsts:lispkgmangthereisacircleintherequiredpackages
 msgid "There is a circle in the required packages. See package graph."
 msgstr "Îáíàðóæåí öèêë çàâèñèìîñòåé ïàêåòîâ. Ñìîòðèòå äèàãðàììó ïàêåòîâ."
@@ -5618,6 +5630,14 @@ msgstr "
 msgid "There is a file with the same name and a similar extension ond disk%sFile: %s%sAmbigious File: %s%s%sDelete ambigious file?"
 msgstr "Íà äèñêå åñòü ôàéë ñ òàêèì æå èìåíåì è ïîõîæèì ðàñøèðåíèåì%sÔàéë: %s%sÏîõîæèé ôàéë: %s%s%sÓäàëèòü âòîðîé ôàéë?"
 
+#: lazarusidestrconsts:lispkgmangthereisafpcunitwiththesamenameasapackage
+msgid "There is a FPC unit with the same name as a package:%s%s%s%s%s%s"
+msgstr ""
+
+#: lazarusidestrconsts:lispkgmangthereisafpcunitwiththesamenamefrom
+msgid "There is a FPC unit with the same name:%s%s%s%s%s from %s%s%s"
+msgstr ""
+
 #: lazarusidestrconsts:lisexttoolthereisamaximumoftools
 msgid "There is a maximum of %s tools."
 msgstr "Äîïóñêàåòñÿ ìàêñèìóì %s èíñòðóìåíòîâ."
@@ -5626,6 +5646,10 @@ msgstr "
 msgid "There is a unit with the name %s%s%s in the project.%sPlz choose a different name"
 msgstr "Â ïðîåêòå åñòü ìîäóëü ñ èìåíåì %s%s%s.%sÂûáåðèòå äðóãîå èìÿ"
 
+#: lazarusidestrconsts:lispkgmangthereisaunitwiththesamenameasapackage1from2
+msgid "There is a unit with the same name as a package:%s%s1. %s%s%s from %s%s2. %s%s%s%s"
+msgstr ""
+
 #: lazarusidestrconsts:listhereisalreadyaformwiththename
 msgid "There is already a form with the name %s%s%s"
 msgstr "Óæå åñòü ôîðìà ñ èìåíåì %s%s%s"
diff --git a/packager/packagesystem.pas b/packager/packagesystem.pas
index 94631e3812..699655bcdb 100644
--- a/packager/packagesystem.pas
+++ b/packager/packagesystem.pas
@@ -70,6 +70,8 @@ type
   TPkgDeleteEvent = procedure(APackage: TLazPackage) of object;
   TDependencyModifiedEvent = procedure(ADependency: TPkgDependency) of object;
   TEndUpdateEvent = procedure(Sender: TObject; GraphChanged: boolean) of object;
+  TFindFPCUnitEvent = procedure(const UnitName, Directory: string;
+                                var Filename: string) of object;
 
   TLazPackageGraph = class
   private
@@ -134,6 +136,12 @@ type
                                 FirstDependency: TPkgDependency;
                                 var File1, File2: TPkgFile;
                                 var ConflictPkg: TLazPackage): boolean;
+    function FindFPCConflictUnit(APackage: TLazPackage;
+                                FirstDependency: TPkgDependency;
+                                const Directory: string;
+                                OnFindFPCUnit: TFindFPCUnitEvent;
+                                var File1: TPkgFile;
+                                var ConflictPkg: TLazPackage): boolean;
     function FindFileInAllPackages(const TheFilename: string;
                                 ResolveLinks, IgnoreDeleted: boolean): TPkgFile;
     function FindLowestPkgNodeByName(const PkgName: string): TAVLTreeNode;
@@ -1273,17 +1281,10 @@ function TLazPackageGraph.FindUnsavedDependencyPath(APackage: TLazPackage;
     end;
   end;
 
-var
-  i: Integer;
-  Pkg: TLazPackage;
 begin
   Result:=nil;
   if (Count=0) or (APackage=nil) then exit;
-  // mark all packages as not visited
-  for i:=FItems.Count-1 downto 0 do begin
-    Pkg:=TLazPackage(FItems[i]);
-    Pkg.Flags:=Pkg.Flags-[lpfVisited];
-  end;
+  MarkAllPackagesAsNotVisited;
   if APackage<>nil then begin
     APackage.Flags:=APackage.Flags+[lpfVisited];
     FirstDependency:=APackage.FirstRequiredDependency;
@@ -1449,6 +1450,68 @@ begin
   Result:=false;
 end;
 
+function TLazPackageGraph.FindFPCConflictUnit(APackage: TLazPackage;
+  FirstDependency: TPkgDependency; const Directory: string;
+  OnFindFPCUnit: TFindFPCUnitEvent;
+  var File1: TPkgFile; var ConflictPkg: TLazPackage): boolean;
+  
+  function CheckUnitName(const AnUnitName: string): boolean;
+  var Filename: string;
+  begin
+    Result:=false;
+    if AnUnitName='' then exit;
+    OnFindFPCUnit(AnUnitName,Directory,Filename);
+    Result:=Filename<>'';
+  end;
+  
+  function CheckDependencyList(ADependency: TPkgDependency): boolean; forward;
+
+  function CheckPackage(Pkg1: TLazPackage): boolean;
+  var
+    Cnt: Integer;
+    i: Integer;
+  begin
+    Result:=false;
+    if (Pkg1=nil) or (lpfVisited in Pkg1.Flags)
+    or (Pkg1=FFCLPackage) then exit;
+    Pkg1.Flags:=Pkg1.Flags+[lpfVisited];
+    Result:=CheckUnitName(Pkg1.Name);
+    if Result then begin
+      ConflictPkg:=Pkg1;
+      exit;
+    end;
+    Cnt:=Pkg1.FileCount;
+    for i:=0 to Cnt-1 do begin
+      Result:=CheckUnitName(Pkg1.Files[i].UnitName);
+      if Result then begin
+        File1:=Pkg1.Files[i];
+        exit;
+      end;
+    end;
+    Result:=CheckDependencyList(Pkg1.FirstRequiredDependency);
+  end;
+  
+  function CheckDependencyList(ADependency: TPkgDependency): boolean;
+  begin
+    Result:=false;
+    while ADependency<>nil do begin
+      Result:=CheckPackage(ADependency.RequiredPackage);
+      if Result then exit;
+      ADependency:=ADependency.NextDependency[pdlRequires];
+    end;
+  end;
+
+begin
+  Result:=false;
+  File1:=nil;
+  ConflictPkg:=nil;
+  MarkAllPackagesAsNotVisited;
+  if APackage<>nil then
+    Result:=CheckPackage(APackage)
+  else
+    Result:=CheckDependencyList(FirstDependency);
+end;
+
 function TLazPackageGraph.GetAutoCompilationOrder(APackage: TLazPackage;
   FirstDependency: TPkgDependency; Policies: TPackageUpdatePolicies): TList;
 // Returns all required auto update packages, including indirect requirements.
@@ -2021,3 +2084,4 @@ initialization
 
 end.
 
+
diff --git a/packager/pkgmanager.pas b/packager/pkgmanager.pas
index 38dbf3e288..494921aa5d 100644
--- a/packager/pkgmanager.pas
+++ b/packager/pkgmanager.pas
@@ -94,6 +94,8 @@ type
     procedure PackageGraphDeletePackage(APackage: TLazPackage);
     procedure PackageGraphDependencyModified(ADependency: TPkgDependency);
     procedure PackageGraphEndUpdate(Sender: TObject; GraphChanged: boolean);
+    procedure PackageGraphFindFPCUnit(const UnitName, Directory: string;
+                                      var Filename: string);
 
     // menu
     procedure MainIDEitmPkgOpenPackageFileClick(Sender: TObject);
@@ -121,7 +123,8 @@ type
                                  FirstDependency: TPkgDependency;
                                  Policies: TPackageUpdatePolicies): TModalResult;
     function CheckPackageGraphForCompilation(APackage: TLazPackage;
-                                 FirstDependency: TPkgDependency): TModalResult;
+                                 FirstDependency: TPkgDependency;
+                                 const Directory: string): TModalResult;
     function DoPreparePackageOutputDirectory(APackage: TLazPackage): TModalResult;
     function DoSavePackageCompiledState(APackage: TLazPackage;
                   const CompilerFilename, CompilerParams: string): TModalResult;
@@ -486,6 +489,12 @@ begin
   end;
 end;
 
+procedure TPkgManager.PackageGraphFindFPCUnit(const UnitName,
+  Directory: string; var Filename: string);
+begin
+  Filename:=CodeToolBoss.DefineTree.FindUnitInUnitLinks(UnitName,Directory,true);
+end;
+
 procedure TPkgManager.mnuConfigCustomCompsClicked(Sender: TObject);
 begin
   ShowConfigureCustomComponents;
@@ -736,7 +745,7 @@ begin
 end;
 
 function TPkgManager.CheckPackageGraphForCompilation(APackage: TLazPackage;
-  FirstDependency: TPkgDependency): TModalResult;
+  FirstDependency: TPkgDependency; const Directory: string): TModalResult;
 var
   PathList: TList;
   Dependency: TPkgDependency;
@@ -793,26 +802,42 @@ begin
       exit;
     end;
 
-    // check for ambigious units
+    // check for ambigious units between packages
     if PackageGraph.FindAmbigiousUnits(APackage,FirstDependency,
       PkgFile1,PkgFile2,ConflictPkg)
     then begin
-      if PkgFile2<>nil then begin
-        s:='There are two units with the same name:'#13
-          +#13
-          +'1. "'+PkgFile1.Filename+'" from '+PkgFile1.LazPackage.IDAsString+#13
-          +'2. "'+PkgFile2.Filename+'" from '+PkgFile2.LazPackage.IDAsString+#13
-          +#13;
-      end else begin
-        s:='There is a unit with the same name as a package:'#13
-          +#13
-          +'1. "'+PkgFile1.Filename+'" from '+PkgFile1.LazPackage.IDAsString+#13
-          +'2. "'+ConflictPkg.IDAsString+#13
-          +#13;
-      end;
-      Result:=MessageDlg('Ambigious units found',s
-          +'Both packages are connected. This means, either one package uses '
-          +'the other, or they are both used by a third package.',
+      if (PkgFile1<>nil) and (PkgFile2<>nil) then begin
+        s:=Format(lisPkgMangThereAreTwoUnitsWithTheSameName1From2From, [#13,
+          #13, '"', PkgFile1.Filename, '"', PkgFile1.LazPackage.IDAsString,
+          #13, '"', PkgFile2.Filename, '"', PkgFile2.LazPackage.IDAsString,
+          #13, #13]);
+      end else if (PkgFile1<>nil) and (ConflictPkg<>nil) then begin
+        s:=Format(lisPkgMangThereIsAUnitWithTheSameNameAsAPackage1From2, [#13,
+          #13, '"', PkgFile1.Filename, '"', PkgFile1.LazPackage.IDAsString,
+          #13, '"', ConflictPkg.IDAsString, #13, #13]);
+      end else
+        s:='Internal inconsistency FindAmbigiousUnits: '
+          +'Please report this bug and how you get here.'#13;
+      Result:=MessageDlg(lisPkgMangAmbigiousUnitsFound, Format(
+        lisPkgMangBothPackagesAreConnectedThisMeansEitherOnePackageU, [s]),
+          mtError,[mbCancel,mbAbort],0);
+      exit;
+    end;
+
+    // check for ambigious units between packages
+    if PackageGraph.FindFPCConflictUnit(APackage,FirstDependency,Directory,
+      @PackageGraphFindFPCUnit,PkgFile1,ConflictPkg)
+    then begin
+      if (PkgFile1<>nil) then begin
+        s:=Format(lisPkgMangThereIsAFPCUnitWithTheSameNameFrom, [#13, #13, '"',
+          PkgFile1.Filename, '"', PkgFile1.LazPackage.IDAsString, #13, #13]);
+      end else if (PkgFile1<>nil) and (ConflictPkg<>nil) then begin
+        s:=Format(lisPkgMangThereIsAFPCUnitWithTheSameNameAsAPackage, [#13,
+          #13, '"', ConflictPkg.IDAsString, #13, #13]);
+      end else
+        s:='Internal inconsistency FindFPCConflictUnits: '
+          +'Please report this bug and how you get here.'#13;
+      Result:=MessageDlg(lisPkgMangAmbigiousUnitsFound, s,
           mtError,[mbCancel,mbAbort],0);
       exit;
     end;
@@ -1929,7 +1954,8 @@ begin
   // check graph for circles and broken dependencies
   if not (pcfDoNotCompileDependencies in Flags) then begin
     Result:=CheckPackageGraphForCompilation(nil,
-                                            AProject.FirstRequiredDependency);
+                                            AProject.FirstRequiredDependency,
+                                            AProject.ProjectDirectory);
     if Result<>mrOk then exit;
   end;
   
@@ -1975,7 +2001,7 @@ begin
 
   // check graph for circles and broken dependencies
   if not (pcfDoNotCompileDependencies in Flags) then begin
-    Result:=CheckPackageGraphForCompilation(APackage,nil);
+    Result:=CheckPackageGraphForCompilation(APackage,nil,APackage.Directory);
     if Result<>mrOk then exit;
   end;
   
@@ -2390,7 +2416,8 @@ begin
     end;
 
     // check consistency
-    Result:=CheckPackageGraphForCompilation(APackage,nil);
+    Result:=CheckPackageGraphForCompilation(APackage,nil,
+                                           EnvironmentOptions.LazarusDirectory);
     if Result<>mrOk then exit;
     
     // get all required packages, which will also be auto installed
@@ -2546,7 +2573,8 @@ begin
     end;
     
     // check consistency
-    Result:=CheckPackageGraphForCompilation(nil,FirstAutoInstallDependency);
+    Result:=CheckPackageGraphForCompilation(nil,FirstAutoInstallDependency,
+                                           EnvironmentOptions.LazarusDirectory);
     if Result<>mrOk then exit;
 
     // save all open files