diff --git a/lib/redmine_mattermost/listener.rb b/lib/redmine_mattermost/listener.rb
index dcf3306..46fad38 100644
--- a/lib/redmine_mattermost/listener.rb
+++ b/lib/redmine_mattermost/listener.rb
@@ -256,6 +256,7 @@ private
 	end
 
 	def mentions text
+		return nil if text.nil?
 		names = extract_usernames text
 		names.present? ? "\nTo: " + names.join(', ') : nil
 	end