diff --git a/lcl/include/comboex.inc b/lcl/include/comboex.inc
index 0c6f2e4fb5..9822fd829c 100644
--- a/lcl/include/comboex.inc
+++ b/lcl/include/comboex.inc
@@ -301,7 +301,7 @@ end;
 procedure TCustomComboBoxEx.AddItem(const Item: String; AnObject: TObject);
 begin
   Insert(ItemsEx.Count, Item);
-  ItemsEx[ItemsEx.Count].Data:=AnObject;
+  ItemsEx[ItemsEx.Count-1].Data:=AnObject;
 end;
 
 procedure TCustomComboBoxEx.AssignItemsEx(AItemsEx: TComboExItems);
diff --git a/lcl/interfaces/cocoa/cocoatextedits.pas b/lcl/interfaces/cocoa/cocoatextedits.pas
index 871e3e8d54..23c6d5d5f2 100644
--- a/lcl/interfaces/cocoa/cocoatextedits.pas
+++ b/lcl/interfaces/cocoa/cocoatextedits.pas
@@ -300,6 +300,8 @@ type
   { TCocoaReadOnlyComboBoxList }
 
   TCocoaReadOnlyComboBoxList = class(TCocoaComboBoxList)
+  private
+    FId: Integer;
   protected
     FOwner: TCocoaReadOnlyComboBox;
     procedure InsertItem(Index: Integer; const S: string; O: TObject); override;
@@ -323,6 +325,7 @@ type
 
     isOwnerDrawn: Boolean;
     isOwnerMeasure: Boolean;
+    isComboBoxEx: Boolean;
     function acceptsFirstResponder: LCLObjCBoolean; override;
     procedure dealloc; override;
     function lclGetCallback: ICommonCallback; override;
@@ -491,7 +494,16 @@ begin
   mn := FOwner.itemAtIndex(Index);
   if not Assigned(mn) then Exit;
 
-  astr := NSStringUtf8(S);
+  // for TComboBoxEx, the parameter S passed in is always emtpy,
+  // and NSPopUpButton always automatically sets the itemIndex according to
+  // the title, so a unique title needs to be set.
+  if not FOwner.isComboBoxEx then
+    astr := NSStringUtf8(S)
+  else
+  begin
+    astr := NSStringUtf8(FId.ToString);
+    inc(FId);
+  end;
   mn.setTitle(astr);
   astr.release;
 
diff --git a/lcl/interfaces/cocoa/cocoawsstdctrls.pas b/lcl/interfaces/cocoa/cocoawsstdctrls.pas
index ba4ccada67..e7d9335f7b 100644
--- a/lcl/interfaces/cocoa/cocoawsstdctrls.pas
+++ b/lcl/interfaces/cocoa/cocoawsstdctrls.pas
@@ -1880,6 +1880,7 @@ begin
   begin
     rocmb := NSView(TCocoaReadOnlyComboBox.alloc).lclInitWithCreateParams(AParams);
     if not Assigned(rocmb) then Exit;
+    rocmb.isComboBoxEx:= not (AWinControl is TComboBox);
     rocmb.list:=TCocoaReadOnlyComboBoxList.Create(rocmb);
     rocmb.setTarget(rocmb);
     rocmb.setAction(objcselector('comboboxAction:'));