diff --git a/lcl/comctrls.pp b/lcl/comctrls.pp
index e7da9ccfe2..a28b185abc 100644
--- a/lcl/comctrls.pp
+++ b/lcl/comctrls.pp
@@ -839,7 +839,6 @@ type
     procedure AdjustDisplayRectWithBorder(var ARect: TRect); virtual;
     procedure AdjustClientRect(var ARect: TRect); override;
     function CreateTabNoteBookStrings: TTabControlNoteBookStrings; virtual;
-    function GetClientOrigin: TPoint; override;
   public
     constructor Create(TheOwner: TComponent); override;
     destructor Destroy; override;
diff --git a/lcl/include/tabcontrol.inc b/lcl/include/tabcontrol.inc
index c75a8ab64e..dde6cd41b9 100644
--- a/lcl/include/tabcontrol.inc
+++ b/lcl/include/tabcontrol.inc
@@ -758,11 +758,6 @@ begin
   Result := TTabControlNoteBookStrings.Create(Self);
 end;
 
-function TTabControl.GetClientOrigin: TPoint;
-begin
-  Result := TTabControlNoteBookStrings(FTabs).FNoteBook.ClientOrigin;
-end;
-
 constructor TTabControl.Create(TheOwner: TComponent);
 begin
   FTabControlCreating:=true;
@@ -794,13 +789,17 @@ begin
 end;
 
 function TTabControl.IndexOfTabAt(X, Y: Integer): Integer;
+var
+  Offs: TPoint;
 begin
-  Result:=TTabControlStrings(FTabs).IndexOfTabAt(X,Y);
+  Offs := TTabControlNoteBookStrings(FTabs).FNoteBook.ClientOrigin;
+  Offs := Offs.Subtract(ClientOrigin);
+  Result:=TTabControlStrings(FTabs).IndexOfTabAt(X-Offs.X, Y-Offs.Y);
 end;
 
 function TTabControl.IndexOfTabAt(P: TPoint): Integer;
 begin
-  Result:=TTabControlStrings(FTabs).IndexOfTabAt(P.x, P.y);
+  Result:=IndexOfTabAt(P.x, P.y);
 end;
 
 function TTabControl.GetHitTestInfoAt(X, Y: Integer): THitTests;