diff --git a/CHANGELOG b/CHANGELOG
index a4bb72a9221..9b66108c160 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -39,6 +39,7 @@ v 8.11.0 (unreleased)
 
 v 8.10.3 (unreleased)
   - Fix hooks missing on imported GitLab projects
+  - Properly abort a merge when merge conflicts occur
 
 v 8.10.2
   - User can now search branches by name. !5144
diff --git a/app/services/merge_requests/merge_service.rb b/app/services/merge_requests/merge_service.rb
index 0dac0614141..b037780c431 100644
--- a/app/services/merge_requests/merge_service.rb
+++ b/app/services/merge_requests/merge_service.rb
@@ -35,7 +35,13 @@ module MergeRequests
       }
 
       commit_id = repository.merge(current_user, merge_request, options)
-      merge_request.update(merge_commit_sha: commit_id)
+
+      if commit_id
+        merge_request.update(merge_commit_sha: commit_id)
+      else
+        merge_request.update(merge_error: 'Conflicts detected during merge')
+        false
+      end
     rescue GitHooksService::PreReceiveError => e
       merge_request.update(merge_error: e.message)
       false
diff --git a/spec/services/merge_requests/merge_service_spec.rb b/spec/services/merge_requests/merge_service_spec.rb
index f5bf3c1e367..8ffebcac698 100644
--- a/spec/services/merge_requests/merge_service_spec.rb
+++ b/spec/services/merge_requests/merge_service_spec.rb
@@ -75,6 +75,17 @@ describe MergeRequests::MergeService, services: true do
 
         expect(merge_request.merge_error).to eq("error")
       end
+
+      it 'aborts if there is a merge conflict' do
+        allow_any_instance_of(Repository).to receive(:merge).and_return(false)
+        allow(service).to receive(:execute_hooks)
+
+        service.execute(merge_request)
+
+        expect(merge_request.open?).to be_truthy
+        expect(merge_request.merge_commit_sha).to be_nil
+        expect(merge_request.merge_error).to eq("Conflicts detected during merge")
+      end
     end
   end
 end