diff --git a/app/controllers/issue_relations_controller.rb b/app/controllers/issue_relations_controller.rb
index abdd60d7c..0bcc8c5e3 100644
--- a/app/controllers/issue_relations_controller.rb
+++ b/app/controllers/issue_relations_controller.rb
@@ -46,7 +46,13 @@ class IssueRelationsController < ApplicationController
     @relation.issue_from = @issue
     @relation.safe_attributes = params[:relation]
     @relation.init_journals(User.current)
-    saved = @relation.save
+
+    begin
+      saved = @relation.save
+    rescue ActiveRecord::RecordNotUnique
+      saved = false
+      @relation.errors.add :base, :taken
+    end
 
     respond_to do |format|
       format.html { redirect_to issue_path(@issue) }