diff --git a/lib/redmine_custom_workflows/patches/issue_relation_patch.rb b/lib/redmine_custom_workflows/patches/issue_relation_patch.rb
index b9f31fc..1e67623 100644
--- a/lib/redmine_custom_workflows/patches/issue_relation_patch.rb
+++ b/lib/redmine_custom_workflows/patches/issue_relation_patch.rb
@@ -36,7 +36,7 @@ module RedmineCustomWorkflows
           alias_method :old_to_s, :to_s
     
           def to_s(issue=nil)
-            block_given? ? old_to_s(issue, &Proc.new) : old_to_s(issue)
+            block_given? ? old_to_s(issue, &Proc.new {}) : old_to_s(issue)
           rescue NoMethodError => e
             if issue_from.present? || issue_to.present?
               raise e