diff --git a/components/codetools/codetoolmanager.pas b/components/codetools/codetoolmanager.pas
index 029d57b584..beb2b49b42 100644
--- a/components/codetools/codetoolmanager.pas
+++ b/components/codetools/codetoolmanager.pas
@@ -207,6 +207,7 @@ type
     function GetPascalCompilerForDirectory(const Directory: string): TPascalCompiler;
     function GetCompilerModeForDirectory(const Directory: string): TCompilerMode;
     function GetCompiledSrcExtForDirectory(const Directory: string): string;
+    function FindUnitInUnitLinks(const Directory, UnitName: string): string;
 
     // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 
@@ -700,6 +701,20 @@ begin
     Result:='.ppw';
 end;
 
+function TCodeToolManager.FindUnitInUnitLinks(const Directory, UnitName: string
+  ): string;
+var
+  Evaluator: TExpressionEvaluator;
+  UnitLinks: string;
+  UnitLinkStart, UnitLinkEnd: integer;
+begin
+  Result:='';
+  Evaluator:=DefineTree.GetDefinesForDirectory(Directory,true);
+  if Evaluator=nil then exit;
+  UnitLinks:=Evaluator[ExternalMacroStart+'UnitLinks'];
+  SearchUnitInUnitLinks(UnitLinks,UnitName,UnitLinkStart,UnitLinkEnd,Result);
+end;
+
 function TCodeToolManager.InitCurCodeTool(Code: TCodeBuffer): boolean;
 var MainCode: TCodeBuffer;
 begin
diff --git a/components/codetools/definetemplates.pas b/components/codetools/definetemplates.pas
index 9ea21bc666..bc4a42c072 100644
--- a/components/codetools/definetemplates.pas
+++ b/components/codetools/definetemplates.pas
@@ -392,7 +392,8 @@ const
   
 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;
 
 implementation
 
@@ -404,7 +405,6 @@ type
     Filename: string;
   end;
 
-
 // some useful functions
 
 function DefineActionNameToAction(const s: string): TDefineAction;
@@ -442,6 +442,69 @@ begin
   Result:=CompareFilenames(DirDef1.Path,DirDef2.Path);
 end;
 
+function SearchUnitInUnitLinks(const UnitLinks, TheUnitName: string;
+  var UnitLinkStart, UnitLinkEnd: integer; var Filename: string): boolean;
+var
+  UnitLinkLen: integer;
+begin
+  Result:=false;
+  Filename:='';
+  if TheUnitName='' then exit;
+  {$IFDEF ShowTriedFiles}
+  writeln('TFindDeclarationTool.FindUnitSource.SearchUnitInUnitLinks length(UnitLinks)=',length(UnitLinks));
+  {$ENDIF}
+  if UnitLinkStart<1 then
+    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
+      {$IFDEF ShowTriedFiles}
+      writeln('  unit "',copy(UnitLinks,UnitLinkStart,UnitLinkEnd-UnitLinkStart),'" ',CompareSubStrings(TheUnitName,UnitLinks,1,
+        UnitLinkStart,UnitLinkLen,false));
+      {$ENDIF}
+      if (UnitLinkLen=length(TheUnitName))
+      and (AnsiStrLIComp(PChar(TheUnitName),@UnitLinks[UnitLinkStart],
+           UnitLinkLen)=0)
+      then begin
+        // unit found -> parse filename
+        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);
+          if FileExists(Filename) then begin
+            Result:=true;
+            exit;
+          end;
+          // try also different extensions
+          if CompareFileExt(Filename,'.pp',false)=0 then
+            Filename:=ChangeFileExt(Filename,'.pas')
+          else
+            Filename:=ChangeFileExt(Filename,'.pp');
+          if FileExists(Filename) then begin
+            Result:=true;
+            exit;
+          end;
+        end;
+      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;
+end;
 
 { TDefineTemplate }
 
diff --git a/packager/basepkgmanager.pas b/packager/basepkgmanager.pas
index e1a739a474..6db96d024b 100644
--- a/packager/basepkgmanager.pas
+++ b/packager/basepkgmanager.pas
@@ -108,6 +108,8 @@ type
                       Flags: TPkgCompileFlags): TModalResult; virtual; abstract;
     function OnRenameFile(const OldFilename,
                           NewFilename: string): TModalResult; virtual; abstract;
+    function FindIncludeFileInProjectDependencies(Project1: TProject;
+                          const Filename: string): string; virtual; abstract;
 
     function OnProjectInspectorOpen(Sender: TObject): boolean; virtual; abstract;
     function DoCompileAutoInstallPackages(Flags: TPkgCompileFlags
diff --git a/packager/packagesystem.pas b/packager/packagesystem.pas
index c4648b39f3..3e37d9fe52 100644
--- a/packager/packagesystem.pas
+++ b/packager/packagesystem.pas
@@ -884,7 +884,9 @@ begin
     // add unit paths
     UsageOptions.UnitPath:=
       '$(LazarusDir)/lcl/units;$(LazarusDir)/lcl/units/$(LCLWidgetType)';
-      
+    // add include path
+    CompilerOptions.IncludeFiles:='$(LazarusDir)/lcl/include';
+
     // use the lcl/units/allunits.o file as indicator,
     // if LCL has been recompiled
     OutputStateFile:='$(LazarusDir)/lcl/units/allunits.o';
diff --git a/packager/pkgmanager.pas b/packager/pkgmanager.pas
index bd577483a5..2efaf4c4c7 100644
--- a/packager/pkgmanager.pas
+++ b/packager/pkgmanager.pas
@@ -154,6 +154,8 @@ type
     function GetPublishPackageDir(APackage: TLazPackage): string;
     function OnRenameFile(const OldFilename,
                           NewFilename: string): TModalResult; override;
+    function FindIncludeFileInProjectDependencies(Project1: TProject;
+                          const Filename: string): string; override;
 
     // package graph
     function AddPackageToGraph(APackage: TLazPackage; Replace: boolean): TModalResult;
@@ -2097,6 +2099,40 @@ begin
   Result:=mrOk;
 end;
 
+{------------------------------------------------------------------------------
+  function TPkgManager.FindIncludeFileInProjectDependencies(Project1: TProject;
+    const Filename: string): string;
+    
+  Search filename in the include paths of all required packages
+------------------------------------------------------------------------------}
+function TPkgManager.FindIncludeFileInProjectDependencies(Project1: TProject;
+  const Filename: string): string;
+var
+  APackage: TLazPackage;
+  IncPath: String;
+  PkgList: Tlist;
+  i: Integer;
+begin
+  Result:='';
+  if FilenameIsAbsolute(Filename) then begin
+    Result:=Filename;
+    exit;
+  end;
+  PkgList:=nil;
+  PackageGraph.GetAllRequiredPackages(Project1.FirstRequiredDependency,PkgList);
+  if PkgList=nil then exit;
+  try
+    for i:=0 to PkgList.Count-1 do begin
+      APackage:=TLazPackage(PkgList[i]);
+      IncPath:=APackage.CompilerOptions.IncludeFiles;
+      Result:=SearchFileInPath(Filename,APackage.Directory,IncPath,';',[]);
+      if Result<>'' then exit;
+    end;
+  finally
+    PkgList.Free;
+  end;
+end;
+
 function TPkgManager.DoAddActiveUnitToAPackage: TModalResult;
 var
   ActiveSourceEditor: TSourceEditor;