diff --git a/Public/js/views/expression_field.js b/Public/js/views/expression_field.js
index f08a2a7..52898f2 100644
--- a/Public/js/views/expression_field.js
+++ b/Public/js/views/expression_field.js
@@ -29,7 +29,7 @@ export class ExpressionField extends EventDispatcher {
   }
 
   set error(error) {
-    if (error) {
+    if (error.length) {
       let message = "";
       if (typeof error === "string" || error instanceof String) {
         const errorMessage = Utils.htmlSafe(error);