diff --git a/RhSolutions.AddIn/Controllers/RibbonController.cs b/RhSolutions.AddIn/Controllers/RibbonController.cs
index b5edde0..03777cc 100644
--- a/RhSolutions.AddIn/Controllers/RibbonController.cs
+++ b/RhSolutions.AddIn/Controllers/RibbonController.cs
@@ -84,7 +84,7 @@ public class RibbonController : ExcelRibbon
 
     public bool GetConvertEnabled(IRibbonControl control) => _workbookIsValid;
     public bool GetDxfEnabled(IRibbonControl control) => _workbookIsValid;
-    public bool GetGuessEnabled(IRibbonControl control) => RhSolutionsAddIn.Excel.ActiveWorkbook == null ? false : !_workbookIsValid;
+    public bool GetGuessEnabled(IRibbonControl control) => RhSolutionsAddIn.Excel.ActiveWorkbook != null && !_workbookIsValid;
 
     public bool GetExportEnabled(IRibbonControl control)
     {