diff --git a/app/controllers/projects/merge_requests_controller.rb b/app/controllers/projects/merge_requests_controller.rb
index e24a670631f..a2225cc8343 100644
--- a/app/controllers/projects/merge_requests_controller.rb
+++ b/app/controllers/projects/merge_requests_controller.rb
@@ -564,7 +564,7 @@ class Projects::MergeRequestsController < Projects::ApplicationController
   def define_pipelines_vars
     @pipelines = @merge_request.all_pipelines
     @pipeline = @merge_request.pipeline
-    @statuses = @pipeline.statuses.relevant if @pipeline.present?
+    @statuses_count = @pipeline.present? ? @pipeline.statuses.relevant.count : 0
   end
 
   def define_new_vars
diff --git a/app/models/merge_request.rb b/app/models/merge_request.rb
index 69c6aa700d6..38d8c15e6b0 100644
--- a/app/models/merge_request.rb
+++ b/app/models/merge_request.rb
@@ -781,7 +781,7 @@ class MergeRequest < ActiveRecord::Base
   end
 
   def all_pipelines
-    return unless source_project
+    return Ci::Pipeline.none unless source_project
 
     @all_pipelines ||= source_project.pipelines
       .where(sha: all_commits_sha, ref: source_branch)
diff --git a/app/views/projects/merge_requests/_new_submit.html.haml b/app/views/projects/merge_requests/_new_submit.html.haml
index 9c6f562f7db..4a08ed045f4 100644
--- a/app/views/projects/merge_requests/_new_submit.html.haml
+++ b/app/views/projects/merge_requests/_new_submit.html.haml
@@ -34,10 +34,11 @@
           = link_to url_for(params), data: {target: 'div#pipelines', action: 'pipelines', toggle: 'tab'} do
             Pipelines
             %span.badge= @pipelines.size
+      - if @pipeline.present?
         %li.builds-tab
           = link_to url_for(params), data: {target: 'div#builds', action: 'builds', toggle: 'tab'} do
             Builds
-            %span.badge= @statuses.size
+            %span.badge= @statuses_count
       %li.diffs-tab
         = link_to url_for(params.merge(action: 'new_diffs')), data: {target: 'div#diffs', action: 'new/diffs', toggle: 'tab'} do
           Changes
@@ -48,9 +49,10 @@
         = render "projects/merge_requests/show/commits"
       #diffs.diffs.tab-pane
         - # This tab is always loaded via AJAX
-      - if @pipelines.any?
+      - if @pipeline.present?
         #builds.builds.tab-pane
           = render "projects/merge_requests/show/builds"
+      - if @pipelines.any?
         #pipelines.pipelines.tab-pane
           = render "projects/merge_requests/show/pipelines"
 
@@ -65,5 +67,5 @@
 :javascript
   var merge_request = new MergeRequest({
     action: "#{(@show_changes_tab ? 'new/diffs' : 'new')}",
-    buildsLoaded: "#{@pipelines.any? ? 'true' : 'false'}"
+    buildsLoaded: "#{@pipeline.present? ? 'true' : 'false'}"
   });
diff --git a/app/views/projects/merge_requests/_show.html.haml b/app/views/projects/merge_requests/_show.html.haml
index a497f418c7c..0e2975bd551 100644
--- a/app/views/projects/merge_requests/_show.html.haml
+++ b/app/views/projects/merge_requests/_show.html.haml
@@ -59,15 +59,16 @@
                 = link_to commits_namespace_project_merge_request_path(@project.namespace, @project, @merge_request), data: { target: 'div#commits', action: 'commits', toggle: 'tab' } do
                   Commits
                   %span.badge= @commits_count
-            - if @pipeline
+            - if @pipelines.any?
               %li.pipelines-tab
                 = link_to pipelines_namespace_project_merge_request_path(@project.namespace, @project, @merge_request), data: { target: '#pipelines', action: 'pipelines', toggle: 'tab' } do
                   Pipelines
                   %span.badge= @pipelines.size
+            - if @pipeline.present?
               %li.builds-tab
                 = link_to builds_namespace_project_merge_request_path(@project.namespace, @project, @merge_request), data: { target: '#builds', action: 'builds', toggle: 'tab' } do
                   Builds
-                  %span.badge= @statuses.size
+                  %span.badge= @statuses_count
             %li.diffs-tab
               = link_to diffs_namespace_project_merge_request_path(@project.namespace, @project, @merge_request), data: { target: 'div#diffs', action: 'diffs', toggle: 'tab' } do
                 Changes
diff --git a/changelogs/unreleased/24860-actionview-template-error-undefined-method-size-for-nil-nilclass.yml b/changelogs/unreleased/24860-actionview-template-error-undefined-method-size-for-nil-nilclass.yml
new file mode 100644
index 00000000000..4b4aea79380
--- /dev/null
+++ b/changelogs/unreleased/24860-actionview-template-error-undefined-method-size-for-nil-nilclass.yml
@@ -0,0 +1,4 @@
+---
+title: Prevent error when submitting a merge request and pipeline is not defined
+merge_request: 7707
+author:
diff --git a/spec/views/projects/merge_requests/_new_submit.html.haml_spec.rb b/spec/views/projects/merge_requests/_new_submit.html.haml_spec.rb
new file mode 100644
index 00000000000..4f698a34ab5
--- /dev/null
+++ b/spec/views/projects/merge_requests/_new_submit.html.haml_spec.rb
@@ -0,0 +1,31 @@
+require 'spec_helper'
+
+describe 'projects/merge_requests/_new_submit.html.haml', :view do
+  let(:merge_request) { create(:merge_request) }
+  let!(:pipeline) { create(:ci_empty_pipeline) }
+
+  before do
+    controller.prepend_view_path('app/views/projects')
+
+    assign(:merge_request, merge_request)
+    assign(:commits, merge_request.commits)
+    assign(:project, merge_request.target_project)
+
+    allow(view).to receive(:can?).and_return(true)
+    allow(view).to receive(:url_for).and_return('#')
+    allow(view).to receive(:current_user).and_return(merge_request.author)
+  end
+
+  context 'when there are pipelines for merge request but no pipeline for last commit' do
+    before do
+      assign(:pipelines, Ci::Pipeline.all)
+      assign(:pipeline, nil)
+    end
+
+    it 'shows <<Pipelines>> tab and hides <<Builds>> tab' do
+      render
+      expect(rendered).to have_text('Pipelines 1')
+      expect(rendered).not_to have_text('Builds')
+    end
+  end
+end