diff --git a/assets/js/src/help-tooltip.jsx b/assets/js/src/help-tooltip.jsx
index e60550652e..bb2ada2d26 100644
--- a/assets/js/src/help-tooltip.jsx
+++ b/assets/js/src/help-tooltip.jsx
@@ -14,7 +14,7 @@ function Tooltip(props) {
     tooltip = (<span
       style={{
         pointerEvents: 'all',
-        maxWidth: '400',
+        maxWidth: '400px',
         display: 'inline-block',
       }}
     >