diff --git a/js/js.translator/testData/kotlin_lib.js b/js/js.translator/testData/kotlin_lib.js
index ed6df120ce5..0bd926b3326 100644
--- a/js/js.translator/testData/kotlin_lib.js
+++ b/js/js.translator/testData/kotlin_lib.js
@@ -431,7 +431,7 @@
                 else {
                     builder += ", ";
                 }
-                builder += iterator.next();
+                builder += Kotlin.toString(iterator.next());
             }
             builder += "]";
             return builder;