diff --git a/lib/javascript-static.js b/lib/javascript-static.js
index e0bb81627c2..087d399c8fd 100644
--- a/lib/javascript-static.js
+++ b/lib/javascript-static.js
@@ -479,7 +479,7 @@ M.util.init_colour_picker = function(Y, id, previewconf) {
 
                 if (typeof(previewconf) === 'object' && previewconf !== null) {
                     Y.one('#'+id+'_preview').on('click', function(e){
-                        if (Y.Lang.isString()) {
+                        if (Y.Lang.isString(previewconf.selector)) {
                             Y.all(previewconf.selector).setStyle(previewconf.style, this.input.get('value'));
                         } else {
                             for (var i in previewconf.selector) {