diff --git a/lib/simple_navigation_bootstrap/bootstrap4.rb b/lib/simple_navigation_bootstrap/bootstrap4.rb
index 30f1f31..d37c457 100644
--- a/lib/simple_navigation_bootstrap/bootstrap4.rb
+++ b/lib/simple_navigation_bootstrap/bootstrap4.rb
@@ -19,7 +19,7 @@ def navigation_class
       end
 
 
-      def container_class(level)
+      def container_class(_level)
         remove_navigation_class = options.fetch(:remove_navigation_class) { false }
         remove_navigation_class ? '' : ['nav', navigation_class].compact
       end