diff --git a/lcl/interfaces/cocoa/cocoaprivate.pp b/lcl/interfaces/cocoa/cocoaprivate.pp
index 40a60953ca..5fb422ff21 100644
--- a/lcl/interfaces/cocoa/cocoaprivate.pp
+++ b/lcl/interfaces/cocoa/cocoaprivate.pp
@@ -412,6 +412,7 @@ type
   end;
 
 procedure SetViewDefaults(AView: NSView);
+function CheckMainThread: Boolean;
 
 implementation
 
@@ -421,6 +422,11 @@ begin
   AView.setAutoresizingMask(NSViewMinYMargin or NSViewMaxXMargin);
 end;
 
+function CheckMainThread: Boolean;
+begin
+  Result := NSThread.currentThread.isMainThread;
+end;
+
 { TCocoaPanel }
 
 function TCocoaPanel.windowShouldClose(sender: id): LongBool;
@@ -893,7 +899,8 @@ end;
 procedure TCocoaCustomControl.drawRect(dirtyRect: NSRect);
 begin
   inherited drawRect(dirtyRect);
-  callback.Draw(NSGraphicsContext.currentContext, bounds, dirtyRect);
+  if CheckMainThread then
+    callback.Draw(NSGraphicsContext.currentContext, bounds, dirtyRect);
 end;
 
 function TCocoaCustomControl.lclGetCallback: ICommonCallback;
diff --git a/lcl/interfaces/cocoa/cocoawscommon.pas b/lcl/interfaces/cocoa/cocoawscommon.pas
index a031e7b12f..7908ec4350 100644
--- a/lcl/interfaces/cocoa/cocoawscommon.pas
+++ b/lcl/interfaces/cocoa/cocoawscommon.pas
@@ -777,7 +777,6 @@ end;
 
 function TLCLCommonCallback.DeliverMessage(var Msg): LRESULT;
 begin
-//  WriteLn('Delivering message to target: ', PtrInt(Target), ' ', Target.ClassName);
   Result := LCLMessageGlue.DeliverMessage(Target, Msg);
 end;