diff --git a/app/controllers/application_controller.rb b/app/controllers/application_controller.rb
index bbeaeb7694e..eeabcc0c9bb 100644
--- a/app/controllers/application_controller.rb
+++ b/app/controllers/application_controller.rb
@@ -12,7 +12,9 @@ class ApplicationController < ActionController::Base
   include WorkhorseHelper
   include EnforcesTwoFactorAuthentication
   include WithPerformanceBar
-  include InvalidUTF8ErrorHandler
+  # this can be removed after switching to rails 5
+  # https://gitlab.com/gitlab-org/gitlab-ce/issues/51908
+  include InvalidUTF8ErrorHandler unless Gitlab.rails5?
 
   before_action :authenticate_sessionless_user!
   before_action :authenticate_user!
diff --git a/spec/controllers/application_controller_spec.rb b/spec/controllers/application_controller_spec.rb
index a8556771edd..be3fc832008 100644
--- a/spec/controllers/application_controller_spec.rb
+++ b/spec/controllers/application_controller_spec.rb
@@ -685,22 +685,34 @@ describe ApplicationController do
     end
 
     context 'html' do
-      it 'renders 412' do
-        get :index, text: "hi \255"
+      subject { get :index, text: "hi \255" }
 
-        expect(response).to have_gitlab_http_status(412)
-        expect(response).to render_template :precondition_failed
+      it 'renders 412' do
+        if Gitlab.rails5?
+          expect { subject }.to raise_error(ActionController::BadRequest)
+        else
+          subject
+
+          expect(response).to have_gitlab_http_status(412)
+          expect(response).to render_template :precondition_failed
+        end
       end
     end
 
     context 'js' do
+      subject { get :index, text: "hi \255", format: :js }
+
       it 'renders 412' do
-        get :index, text: "hi \255", format: :js
+        if Gitlab.rails5?
+          expect { subject }.to raise_error(ActionController::BadRequest)
+        else
+          subject
 
-        json_response = JSON.parse(response.body)
+          json_response = JSON.parse(response.body)
 
-        expect(response).to have_gitlab_http_status(412)
-        expect(json_response['error']).to eq('Invalid UTF-8')
+          expect(response).to have_gitlab_http_status(412)
+          expect(json_response['error']).to eq('Invalid UTF-8')
+        end
       end
     end
   end