diff --git a/src/gui/fpg_stylemanager.pas b/src/gui/fpg_stylemanager.pas
index b7c355733..324172c85 100644
--- a/src/gui/fpg_stylemanager.pas
+++ b/src/gui/fpg_stylemanager.pas
@@ -147,7 +147,7 @@ function TfpgStyleManager.SetStyle(const AStyleName: string): boolean;
     end;
   end;
 
-  Assert(FDefaultStyleType <> AStyleName,
+  Assert(FDefaultStyleType = AStyleName,
       Format('<%s> does not identify a registered style class.', [AStyleName]));
 end;