diff --git a/firestore.rules b/firestore.rules
index 9d10dc61..f758a19c 100644
--- a/firestore.rules
+++ b/firestore.rules
@@ -10,7 +10,8 @@ service cloud.firestore {
 
     match /contracts/{contractId} {
       allow read;
-      allow update: if resource.data.creatorId == request.auth.uid && request.resource.data.keys().hasOnly(["description"]);
+      allow update: if resource.data.creatorId == request.auth.uid && request.resource.data.diff(resource.data).affectedKeys()
+        .hasOnly(['description']);
       allow delete: if resource.data.creatorId == request.auth.uid;
     }