diff --git a/lib/ace/scrollbar.js b/lib/ace/scrollbar.js
index a5a31873..55a75b33 100644
--- a/lib/ace/scrollbar.js
+++ b/lib/ace/scrollbar.js
@@ -51,8 +51,11 @@ var ScrollBar = function(parent) {
 
     parent.appendChild(this.element);
 
+    // in OSX lion the scrollbars appear to have no width. In this case resize
+    // the to show the scrollbar but still pretend that the scrollbar has a width
+    // of 0px
     this.width = dom.scrollbarWidth();
-    this.element.style.width = this.width + "px";
+    this.element.style.width = (this.width || 15) + "px";
 
     event.addListener(this.element, "scroll", this.onScroll.bind(this));
 };