diff --git a/knockout.activity.js b/knockout.activity.js
index 8d9c572..c234e1c 100644
--- a/knockout.activity.js
+++ b/knockout.activity.js
@@ -156,7 +156,7 @@
                         rule += p1 + value + p2 + value;
                     }
                     rule += '100% { -webkit-transform:rotate(100deg); }\n}';
-                    document.styleSheets[0].insertRule(rule);
+                    document.styleSheets[0].insertRule(rule, document.styleSheets[0].cssRules.length);
                     animations[steps] = name;
                 }
                 el.css('-webkit-animation', animations[steps] + ' ' + duration + 's linear infinite');