diff --git a/app/controllers/projects/milestones_controller.rb b/app/controllers/projects/milestones_controller.rb
index f4ee7427d29f831a55f213428fbfeece0b4a4b4e..39cd579cce5b75b38eaa0016e7d8712c9496118a 100644
--- a/app/controllers/projects/milestones_controller.rb
+++ b/app/controllers/projects/milestones_controller.rb
@@ -81,7 +81,7 @@ class Projects::MilestonesController < Projects::ApplicationController
   protected
 
   def milestone
-    @milestone ||= @project.milestones.find(params[:id])
+    @milestone ||= @project.milestones.find_by_iid!(params[:id])
   end
 
   def authorize_admin_milestone!
diff --git a/spec/models/milestone_spec.rb b/spec/models/milestone_spec.rb
index dfda1c873795d33ffb60539cb0b5bfcea550a343..23b8a4aeae5caa153be3a84aa844cceafe364999 100644
--- a/spec/models/milestone_spec.rb
+++ b/spec/models/milestone_spec.rb
@@ -25,6 +25,7 @@ describe Milestone do
   end
 
   describe "Validation" do
+    before { subject.stub(set_iid: false) }
     it { should validate_presence_of(:title) }
     it { should validate_presence_of(:project) }
   end