diff --git a/src/js/easymde.js b/src/js/easymde.js
index ccc04a0..f4a0c70 100644
--- a/src/js/easymde.js
+++ b/src/js/easymde.js
@@ -239,7 +239,9 @@ function createToolbarButton(options, enableActions, enableTooltips, shortcuts,
 
     if (options.attributes) {
         for (var attribute in options.attributes) {
-            el.setAttribute(attribute, options.attributes[attribute]);
+            if (Object.prototype.hasOwnProperty.call(options.attributes, attribute)) {
+                el.setAttribute(attribute, options.attributes[attribute]);
+            }
         }
     }