diff --git a/lib/plugins/acts_as_event/lib/acts_as_event.rb b/lib/plugins/acts_as_event/lib/acts_as_event.rb
index 42673cde7..143edd58a 100644
--- a/lib/plugins/acts_as_event/lib/acts_as_event.rb
+++ b/lib/plugins/acts_as_event/lib/acts_as_event.rb
@@ -72,7 +72,7 @@ module Redmine
         def event_url(options = {})
           option = event_options[:url]
           if option.is_a?(Proc)
-            option.call(self).merge(options)
+            option.call(self).merge(options) if option.call(self)
           elsif option.is_a?(Hash)
             option.merge(options)
           elsif option.is_a?(Symbol)