diff --git a/CHANGELOG b/CHANGELOG
index 1417cba304..47ea0360d9 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -19,6 +19,7 @@ v 8.7.0 (unreleased)
 v 8.6.5
   - Fix importing from GitHub Enterprise. !3529
   - Check permissions when user attempts to import members from another project. !3535
+  - Only update repository language if it is not set to improve performance. !3556
 
 v 8.6.4
   - Don't attempt to fetch any tags from a forked repo (Stan Hu)
diff --git a/app/services/git_push_service.rb b/app/services/git_push_service.rb
index c007d648dd..21aab6b474 100644
--- a/app/services/git_push_service.rb
+++ b/app/services/git_push_service.rb
@@ -54,12 +54,15 @@ class GitPushService < BaseService
   end
 
   def update_main_language
+    # Performance can be bad so for now only check main_language once
+    # See https://gitlab.com/gitlab-org/gitlab-ce/issues/14937
+    return if @project.main_language.present?
+
+    return unless is_default_branch?
+    return unless push_to_new_branch? || push_to_existing_branch?
+
     current_language = @project.repository.main_language
-
-    unless current_language == @project.main_language
-      return @project.update_attributes(main_language: current_language)
-    end
-
+    @project.update_attributes(main_language: current_language)
     true
   end
 
diff --git a/spec/services/git_push_service_spec.rb b/spec/services/git_push_service_spec.rb
index 8490a729e5..1b48b8ad18 100644
--- a/spec/services/git_push_service_spec.rb
+++ b/spec/services/git_push_service_spec.rb
@@ -165,12 +165,39 @@ describe GitPushService, services: true do
     end
 
     context "after push" do
-      before do
-        @service = execute_service(project, user, @oldrev, @newrev, @ref)
+      def execute
+        execute_service(project, user, @oldrev, @newrev, ref)
       end
 
-      it { expect(@service.update_main_language).to eq(true) }
-      it { expect(project.main_language).to eq("Ruby") }
+      context "to master" do
+        let(:ref) { @ref }
+
+        context 'when main_language is nil' do
+          it 'obtains the language from the repository' do
+            expect(project.repository).to receive(:main_language)
+            execute
+          end
+
+          it 'sets the project main language' do
+            execute
+            expect(project.main_language).to eq("Ruby")
+          end
+        end
+
+        context 'when main_language is already set' do
+          it 'does not check the repository' do
+            execute # do an initial run to simulate lang being preset
+            expect(project.repository).not_to receive(:main_language)
+            execute
+          end
+        end
+      end
+
+      context "to other branch" do
+        let(:ref) { 'refs/heads/feature/branch' }
+
+        it { expect(project.main_language).to eq(nil) }
+      end
     end
   end