diff --git a/manage/config-dialog.js b/manage/config-dialog.js
index 8f2ba6b1..fe665098 100644
--- a/manage/config-dialog.js
+++ b/manage/config-dialog.js
@@ -336,7 +336,7 @@ function configDialog(style) {
       return max;
     }
     // Don't restrict to integer values if step is undefined.
-    if (typeof va.step === 'undefined') {
+    if (!isNumber(va.step)) {
       return value;
     }
     const step = va.step || 1;