diff --git a/lib/utils/javascript_utils.dart b/lib/utils/javascript_utils.dart
index df36ac12..f8182930 100644
--- a/lib/utils/javascript_utils.dart
+++ b/lib/utils/javascript_utils.dart
@@ -76,6 +76,11 @@ class JavascriptUtils {
         }
       }
     }
+    var browserName = getBrowserName();
+    var signatureButton = document.querySelector('.tmail-signature-button');
+    if (browserName === 'Firefox' && signatureButton) {
+      signatureButton.style.userSelect = 'none';
+    }
   ''';
 
   static const String jsHandleRemoveSignature = '''