diff --git a/rsconcept/frontend/src/pages/RSFormPage/EditorRSExpression.tsx b/rsconcept/frontend/src/pages/RSFormPage/EditorRSExpression.tsx
index 07012320..331a5643 100644
--- a/rsconcept/frontend/src/pages/RSFormPage/EditorRSExpression.tsx
+++ b/rsconcept/frontend/src/pages/RSFormPage/EditorRSExpression.tsx
@@ -52,7 +52,7 @@ function EditorRSExpression({
 
   function handleChange(newvalue: string) {
     onChange(newvalue);
-    setIsModified(true);
+    setIsModified(newvalue !== activeCst?.definition_formal);
   }
   
   function handleCheckExpression() {