diff --git a/components/codetools/finddeclarationtool.pas b/components/codetools/finddeclarationtool.pas
index f9909e7843..d1ecba8b56 100644
--- a/components/codetools/finddeclarationtool.pas
+++ b/components/codetools/finddeclarationtool.pas
@@ -7375,7 +7375,7 @@ var
     ExprP:=PChar(Expr);
     for i:=0 to length(UseNames)-1 do begin
       UseNameP:=PChar(UseNames[i]);
-      if CompareIdentifiers(UseNameP,ExprP)=0 then begin
+      if CompareDottedIdentifiers(UseNameP,ExprP)=0 then begin
         DotCount:=GetDotCountInIdentifier(UseNameP);
         if DotCount>BestDotCount then begin
           BestDotCount:=DotCount;
diff --git a/components/codetools/tests/testrefactoring.pas b/components/codetools/tests/testrefactoring.pas
index dabcfa8096..7d0f091d86 100644
--- a/components/codetools/tests/testrefactoring.pas
+++ b/components/codetools/tests/testrefactoring.pas
@@ -73,6 +73,7 @@ type
     procedure TestRenameUsedUnit_Impl;
     procedure TestRenameUsedUnit_FN_KeepShort;
     procedure TestRenameUsedUnit_InFilename;
+    procedure TestRenameUsedUnit_LongestUnitnameWins;
   end;
 
 implementation
@@ -1656,6 +1657,64 @@ begin
   end;
 end;
 
+procedure TTestRefactoring.TestRenameUsedUnit_LongestUnitnameWins;
+var
+  RedUnit, RedGreenUnit, RedGreenBlueUnit: TCodeBuffer;
+begin
+  RedUnit:=CodeToolBoss.CreateFile('red.pas');
+  RedGreenUnit:=CodeToolBoss.CreateFile('red.green.pas');
+  RedGreenBlueUnit:=CodeToolBoss.CreateFile('red.green.blue.pas');
+  try
+    RedUnit.Source:='unit Red;'+LineEnding
+      +'interface'+LineEnding
+      +'var'+LineEnding
+      +'  Red, Green: word;'+LineEnding
+      +'implementation'+LineEnding
+      +'end.';
+
+    RedGreenUnit.Source:='unit Red.Green;'+LineEnding
+      +'interface'+LineEnding
+      +'var'+LineEnding
+      +'  Green, Blue: word;'+LineEnding
+      +'implementation'+LineEnding
+      +'end.';
+
+    RedGreenBlueUnit.Source:='unit Red.Green.Blue;'+LineEnding
+      +'interface'+LineEnding
+      +'var'+LineEnding
+      +'  Blue: word;'+LineEnding
+      +'implementation'+LineEnding
+      +'end.';
+
+    Add([
+    'program test1;',
+    '{$mode objfpc}{$H+}',
+    'uses Red, Red.Green, Red.Green.Blue;',
+    'begin',
+    '  red.red:=1;',
+    '  red.green.green:=2;',
+    '  red.green.blue.blue:=3;',
+    'end.',
+    '']);
+    RenameUsedUnitRefs(RedGreenUnit,'&End','end.pas');
+    CheckDiff(Code,[
+    'program test1;',
+    '{$mode objfpc}{$H+}',
+    'uses Red, &End, Red.Green.Blue;',
+    'begin',
+    '  red.red:=1;',
+    '  &End.green:=2;',
+    '  red.green.blue.blue:=3;',
+    'end.',
+    '']);
+
+  finally
+    RedUnit.IsDeleted:=true;
+    RedGreenUnit.IsDeleted:=true;
+    RedGreenBlueUnit.IsDeleted:=true;
+  end;
+end;
+
 initialization
   RegisterTests([TTestRefactoring]);
 end.