diff --git a/src/Posting/Captcha.cache.coffee b/src/Posting/Captcha.cache.coffee
index 9255b7ab5..1f6f05b49 100644
--- a/src/Posting/Captcha.cache.coffee
+++ b/src/Posting/Captcha.cache.coffee
@@ -20,6 +20,7 @@ Captcha.cache =
     captchaCount < postsCount
 
   sync: (captchas=[]) ->
+    captchas = [] unless captchas instanceof Array
     @captchas = captchas
     @count()