diff --git a/demo/styles.css b/demo/styles.css
index 44ab6810..ff6a749f 100644
--- a/demo/styles.css
+++ b/demo/styles.css
@@ -27,6 +27,12 @@ body {
     background-position: 4px center;
 }
 
+.ace_gutter-cell.ace_warning {
+    background-image: url("icons/warning_obj.gif");
+    background-repeat: no-repeat;
+    background-position: 4px center;
+}
+
 #controls {
     width: 100%;
     height: 55px;