diff --git a/flow-server/src/main/java/com/vaadin/flow/server/communication/IndexHtmlRequestHandler.java b/flow-server/src/main/java/com/vaadin/flow/server/communication/IndexHtmlRequestHandler.java
index 1d22fedf738..7c5ad292a69 100644
--- a/flow-server/src/main/java/com/vaadin/flow/server/communication/IndexHtmlRequestHandler.java
+++ b/flow-server/src/main/java/com/vaadin/flow/server/communication/IndexHtmlRequestHandler.java
@@ -287,7 +287,7 @@ private void catchErrorsInDevMode(Document indexDocument) {
                 + //
                 "};" + //
                 "window.addEventListener('unhandledrejection', e => {" + //
-                "    window.Vaadin.ConsoleErrors.push([e.reason]);" + //
+                "    window.Vaadin.ConsoleErrors.push(e.reason);" + //
                 "});" //
         );
     }