Specify type attribute of custom variable

webpaste.el

@@ -47,7 +47,8 @@ provider priority for which order which provider should be tried when used."
   "Define provider priority of which providers to try in which order.
 This variable should be a list of strings and if it isn't defined it will
 default to all providers in order defined in ‘webpaste-providers’ list."
-  :group 'webpaste)
+  :group 'webpaste
+  :type '(repeat string))
 
 
 (defvar webpaste-tested-providers ()
@@ -111,7 +112,9 @@ each run.")
 Consists of provider name and lambda function to do the actuall call to the
 provider.  The lamda should call ‘webpaste-return-url’ with resulting url to
 return it to the user."
-  :group 'webpaste)
+  :group 'webpaste
+  :type  '(alist :key-type (string :tag "provider name")
+                 :value-type (function :tag "lambda function to the provider")))
 
 
 ;; Function we use to return the RETURNED-URL from the service