diff --git a/components/codetools/basiccodetools.pas b/components/codetools/basiccodetools.pas
index dd728f2e74..7af92c36b0 100644
--- a/components/codetools/basiccodetools.pas
+++ b/components/codetools/basiccodetools.pas
@@ -174,6 +174,9 @@ function CompareAtom(p1, p2: PChar; NestedComments: boolean): integer;
 function CompareStringConstants(p1, p2: PChar): integer; // compare case sensitive
 function CompareComments(p1, p2: PChar; NestedComments: boolean): integer; // compare case insensitive
 
+// dotted identifiers
+function IsDottedIdentifier(const Identifier: string): boolean;
+
 // space and special chars
 function TrimCodeSpace(const ACode: string): string;
 function CodeIsOnlySpace(const ACode: string; FromPos, ToPos: integer): boolean;
@@ -4195,6 +4198,23 @@ begin
   if LengthOfLastLine=0 then ;
 end;
 
+function IsDottedIdentifier(const Identifier: string): boolean;
+var
+  p: PChar;
+begin
+  Result:=false;
+  if Identifier='' then exit;;
+  p:=PChar(Identifier);
+  repeat
+    if not IsIdentStartChar[p^] then exit;
+    inc(p);
+    while IsIdentChar[p^] do inc(p);
+    if p^<>'.' then break;
+    inc(p);
+  until false;
+  Result:=(p-PChar(Identifier))=length(Identifier);
+end;
+
 function TrimCodeSpace(const ACode: string): string;
 // turn all lineends and special chars to space
 // space is combined to one char
diff --git a/components/codetools/pascalreadertool.pas b/components/codetools/pascalreadertool.pas
index 0391835088..15c81a44f3 100644
--- a/components/codetools/pascalreadertool.pas
+++ b/components/codetools/pascalreadertool.pas
@@ -210,6 +210,8 @@ type
     procedure MoveCursorToUsesEnd(UsesNode: TCodeTreeNode);
     procedure ReadNextUsedUnit(out UnitNameRange, InAtom: TAtomPosition);
     procedure ReadPriorUsedUnit(out UnitNameRange, InAtom: TAtomPosition);
+    function ExtractUsedUnitName(UseUnitNode: TCodeTreeNode;
+          InFilename: PAnsiString = nil): string;
 
     // comments
     function FindCommentInFront(const StartPos: TCodeXYPosition;
@@ -2559,6 +2561,28 @@ begin
   until false;
 end;
 
+function TPascalReaderTool.ExtractUsedUnitName(UseUnitNode: TCodeTreeNode;
+  InFilename: PAnsiString): string;
+begin
+  Result:='';
+  if InFilename<>nil then InFilename^:='';
+  if (UseUnitNode=nil) or (UseUnitNode.Desc<>ctnUseUnit) then exit;
+  MoveCursorToCleanPos(UseUnitNode.StartPos);
+  ReadNextAtom;
+  while CurPos.Flag=cafWord do begin
+    if Result<>'' then Result:=Result+'.';
+    Result:=Result+GetAtom;
+    ReadNextAtom;
+    if CurPos.Flag<>cafPoint then break;
+    ReadNextAtom;
+  end;
+  if (InFilename<>nil) and (UpAtomIs('IN')) then begin
+    ReadNextAtom;
+    if not AtomIsStringConstant then exit;
+    InFilename^:=copy(Src,CurPos.StartPos+1,CurPos.EndPos-CurPos.StartPos-2);
+  end;
+end;
+
 function TPascalReaderTool.FindCommentInFront(const StartPos: TCodeXYPosition;
   const CommentText: string; InvokeBuildTree, SearchInParentNode,
   WithCommentBounds, CaseSensitive, IgnoreSpaces, CompareOnlyStart: boolean;
diff --git a/components/codetools/stdcodetools.pas b/components/codetools/stdcodetools.pas
index cf1e14d4a4..8279e5ef3f 100644
--- a/components/codetools/stdcodetools.pas
+++ b/components/codetools/stdcodetools.pas
@@ -402,8 +402,9 @@ var UnitPos, InPos: TAtomPosition;
   NewUsesTerm: string;
 begin
   Result:=false;
-  if (OldUnitName='') or (length(OldUnitName)>255) or (NewUnitName='')
-  or (length(NewUnitName)>255) then exit;
+  if (not IsDottedIdentifier(OldUnitName))
+  or (not IsDottedIdentifier(NewUnitName)) then
+    exit;
   if not FindUnitInAllUsesSections(OldUnitName,UnitPos,InPos) then begin
     //debugln('TStandardCodeTool.RenameUsedUnit not found: ',OldUnitName,' ');
     exit;
@@ -663,7 +664,8 @@ var
     end;
   end;
 
-var LineStart, LineEnd, Indent, InsertPos, InsertToPos, InsertLen: integer;
+var
+  LineStart, LineEnd, Indent, InsertPos, InsertToPos, InsertLen: integer;
   NewUsesTerm: string;
   InsertBehind: Boolean;
   InsertNode: TCodeTreeNode;
@@ -686,9 +688,10 @@ var LineStart, LineEnd, Indent, InsertPos, InsertToPos, InsertLen: integer;
   InsertPosFound: Boolean;
 begin
   Result:=false;
-  if (UsesNode=nil) or (UsesNode.Desc<>ctnUsesSection) or (NewUnitName='')
-  or (length(NewUnitName)>255) or (UsesNode.StartPos<1)
-  or (UsesNode.EndPos<1) then exit;
+  if (UsesNode=nil) or (UsesNode.Desc<>ctnUsesSection)
+  or (UsesNode.StartPos<1) or (UsesNode.EndPos<1)
+  or (not IsDottedIdentifier(NewUnitName))
+  then exit;
   SourceChangeCache.MainScanner:=Scanner;
   Options:=SourceChangeCache.BeautifyCodeOptions;
 
@@ -745,15 +748,7 @@ begin
           BestDiffCnt:=High(integer);
           Node:=FirstNormalUsesNode;
           while Node<>nil do begin
-            MoveCursorToCleanPos(Node.StartPos);
-            ReadNextAtom;
-            AnUnitName:=GetAtom;
-            ReadNextAtom;
-            if UpAtomIs('IN') then begin
-              ReadNextAtom;
-              AnUnitInFilename:=copy(Src,CurPos.StartPos+1,CurPos.EndPos-CurPos.StartPos-2);
-            end else
-              AnUnitInFilename:='';
+            AnUnitName:=ExtractUsedUnitName(Node,@AnUnitInFilename);
             // search unit
             //DebugLn(['TStandardCodeTool.AddUnitToUsesSection Unit=',AnUnitName,' in "',AnUnitInFilename,'"']);
             NewCode:=FindUnitSource(AnUnitName,AnUnitInFilename,false);
@@ -867,10 +862,7 @@ begin
         InsertToPos:=Node.EndPos;
         if (Node=InsertNode) and (not InsertBehind) then
           AddUseUnit(Lines,FirstIndent,Indent,NewUsesTerm);
-        MoveCursorToCleanPos(Node.StartPos);
-        ReadNextAtom;
-        InsertCode:=GetAtom;
-        ReadNextAtom;
+        InsertCode:=ExtractUsedUnitName(Node);
         if UpAtomIs('IN') then begin
           ReadNextAtom;
           InsertCode:=InsertCode+' '+Options.BeautifyKeyWord('in')+' '+GetAtom;