diff --git a/app/models/remote_mirror.rb b/app/models/remote_mirror.rb
index 2fd6ea877e334249d6629cf748126a0a68b6ee0b..a4f7113519ebb49f2088d95b0a86fb141b249769 100644
--- a/app/models/remote_mirror.rb
+++ b/app/models/remote_mirror.rb
@@ -39,9 +39,15 @@ class RemoteMirror < ActiveRecord::Base
       transition failed: :started
     end
 
-    state :started
+    state :started do
+      validates_presence_of :project
+    end
+
     state :finished
-    state :failed
+
+    state :failed do
+      validates_presence_of :project
+    end
 
     after_transition any => :started, do: :schedule_update_job
 
@@ -80,8 +86,9 @@ def mark_for_delete_if_blank_url
   end
 
   def mark_as_failed(error_message)
-    update_fail
-    update_column(:last_error, Gitlab::UrlSanitizer.sanitize(error_message))
+    error_message = errors.full_messages.first unless update_fail
+
+    update_columns(last_error: Gitlab::UrlSanitizer.sanitize(error_message), update_status: 'failed')
   end
 
   def url=(value)
@@ -109,7 +116,7 @@ def safe_url
   private
 
   def url_availability
-    if project.import_url == url && project.mirror?
+    if project && project.import_url == url && project.mirror?
       errors.add(:url, 'is already in use')
     end
   end
diff --git a/app/workers/repository_update_remote_mirror_worker.rb b/app/workers/repository_update_remote_mirror_worker.rb
index fdcae2895ef2f79c7f3dc7130beb5d98d9d1af7c..3993788fb698ac65f2594f81b215b1e23a6230cf 100644
--- a/app/workers/repository_update_remote_mirror_worker.rb
+++ b/app/workers/repository_update_remote_mirror_worker.rb
@@ -10,6 +10,9 @@ def perform(remote_mirror_id)
     begin
       remote_mirror = RemoteMirror.find(remote_mirror_id)
       project       = remote_mirror.project
+
+      return unless project
+
       current_user  = project.creator
       result        = Projects::UpdateRemoteMirrorService.new(project, current_user).execute(remote_mirror)
 
diff --git a/changelogs/unreleased-ee/1165-jej-remote-mirror-validation-failures.yml b/changelogs/unreleased-ee/1165-jej-remote-mirror-validation-failures.yml
new file mode 100644
index 0000000000000000000000000000000000000000..9d9302ca1a0b5ef55695f2e261e0bf0b4b91fd62
--- /dev/null
+++ b/changelogs/unreleased-ee/1165-jej-remote-mirror-validation-failures.yml
@@ -0,0 +1,4 @@
+---
+title: Fix UpdateAllRemoteMirrorsWorker failing when remote mirror has no project
+merge_request: 
+author: 
diff --git a/spec/factories/remote_mirrors.rb b/spec/factories/remote_mirrors.rb
new file mode 100644
index 0000000000000000000000000000000000000000..1e534325d8d07498ae1b4403d1963c552bd4150c
--- /dev/null
+++ b/spec/factories/remote_mirrors.rb
@@ -0,0 +1,6 @@
+FactoryGirl.define do
+  factory :remote_mirror do
+    url 'http://cantbeblank'
+    project
+  end
+end
diff --git a/spec/models/remote_mirror_spec.rb b/spec/models/remote_mirror_spec.rb
index 46bc8affe6498c72bf38c30c68d9592c24c247b6..63241aa111780df71a8e9d112d265fe8841a86de 100644
--- a/spec/models/remote_mirror_spec.rb
+++ b/spec/models/remote_mirror_spec.rb
@@ -84,6 +84,24 @@
     end
   end
 
+  context 'with missing project' do
+    let(:mirror) { create(:remote_mirror, update_status: 'started') }
+
+    before do
+      mirror.update_columns(enabled: true, project_id: nil)
+
+      mirror.reload.mark_as_failed('missing project')
+    end
+
+    it 'sets the last error' do
+      expect(mirror.reload.last_error).to include("Project can't be blank")
+    end
+
+    it 'is marked as failed' do
+      expect(mirror.reload.update_status).to eq('failed')
+    end
+  end
+
   def create_mirror(params)
     project = FactoryGirl.create(:project)
     project.remote_mirrors.create!(params)
diff --git a/spec/workers/repository_update_remote_mirror_worker_spec.rb b/spec/workers/repository_update_remote_mirror_worker_spec.rb
new file mode 100644
index 0000000000000000000000000000000000000000..46d1a2c96cc29bfb47102551d137c31705c3b18c
--- /dev/null
+++ b/spec/workers/repository_update_remote_mirror_worker_spec.rb
@@ -0,0 +1,13 @@
+require 'rails_helper'
+
+describe RepositoryUpdateRemoteMirrorWorker do
+  let(:mirror) { create(:remote_mirror) }
+
+  describe '#perform' do
+    it 'does nothing if project is missing' do
+      mirror.update!(project_id: nil)
+
+      expect(described_class.new.perform(mirror.id)).to be_nil
+    end
+  end
+end
diff --git a/spec/workers/update_all_remote_mirrors_worker_spec.rb b/spec/workers/update_all_remote_mirrors_worker_spec.rb
new file mode 100644
index 0000000000000000000000000000000000000000..3266ee93b568ceef8488bca99643dacb538c0750
--- /dev/null
+++ b/spec/workers/update_all_remote_mirrors_worker_spec.rb
@@ -0,0 +1,25 @@
+require 'rails_helper'
+
+describe UpdateAllRemoteMirrorsWorker do
+  let(:worker) { described_class.new }
+
+  describe '#perform' do
+    context 'stuck mirrors' do
+      let!(:mirror) { create(:remote_mirror, update_status: :started, last_update_at: 1.week.ago) }
+
+      it 'are transitioned to failure state' do
+        worker.perform
+
+        expect(mirror.reload.update_status).to eq('failed')
+      end
+
+      it 'handles enabled mirrors with missing project' do
+        mirror.update_attributes(project_id: nil, enabled: true)
+
+        worker.perform
+
+        expect(mirror.reload.update_status).to eq('failed')
+      end
+    end
+  end
+end