diff --git a/lib/redmine/plugin.rb b/lib/redmine/plugin.rb
index 48d04dcac..7e1fa1763 100644
--- a/lib/redmine/plugin.rb
+++ b/lib/redmine/plugin.rb
@@ -275,7 +275,7 @@ module Redmine
 
     def compare_versions(requirement, current)
       requirement = requirement.split('.').collect(&:to_i)
-      requirement <=> current.slice(0, requirement.size)
+      requirement <=> current.slice(0, requirement.size).collect(&:to_i)
     end
     private :compare_versions