diff --git a/CHANGELOG.md b/CHANGELOG.md
index 3168af372..c60ac0cf0 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,5 @@
+- Fixed an error for Firefox <23 users.
+
 ## 3.7.0 - *2013-08-13*
 
 - **Thread Watcher** improvements:
diff --git a/lib/polyfill.coffee b/lib/polyfill.coffee
index 3cec1905a..6bab699cb 100644
--- a/lib/polyfill.coffee
+++ b/lib/polyfill.coffee
@@ -1,7 +1,9 @@
 Polyfill =
   init: ->
+    <% if (type === 'crx') { %>
     Polyfill.toBlob()
     Polyfill.visibility()
+    <% } %>
   toBlob: ->
     HTMLCanvasElement::toBlob or= (cb) ->
       data = atob @toDataURL()[22..]