diff --git a/app/services/namespaces/projects/assign_runtimes_service.rb b/app/services/namespaces/projects/assign_runtimes_service.rb
index 918a424a..57697e90 100644
--- a/app/services/namespaces/projects/assign_runtimes_service.rb
+++ b/app/services/namespaces/projects/assign_runtimes_service.rb
@@ -24,6 +24,8 @@ def execute
           end
 
           namespace_project.runtimes = runtimes
+          namespace_project.primary_runtime = runtimes.first if runtimes.size == 1
+
           unless namespace_project.save
             t.rollback_and_return! ServiceResponse.error(
               message: 'Failed to assign runtimes to project',
diff --git a/app/services/namespaces/projects/update_service.rb b/app/services/namespaces/projects/update_service.rb
index a68a4728..0e65afb8 100644
--- a/app/services/namespaces/projects/update_service.rb
+++ b/app/services/namespaces/projects/update_service.rb
@@ -21,8 +21,13 @@ def execute
         params[:primary_runtime_id] = params.delete(:primary_runtime)&.id if params.key?(:primary_runtime)
 
         transactional do |t|
-          success = namespace_project.update(params)
-          unless success
+          namespace_project.assign_attributes(params)
+
+          if namespace_project.primary_runtime_changed?
+            UpdateRuntimeCompatibilityJob.perform_later({ namespace_project_id: namespace_project.id })
+          end
+
+          unless namespace_project.save
             t.rollback_and_return! ServiceResponse.error(
               message: 'Failed to update namespace project',
               error_code: :invalid_namespace_project,
diff --git a/spec/services/namespaces/projects/assign_runtimes_service_spec.rb b/spec/services/namespaces/projects/assign_runtimes_service_spec.rb
index ece92755..0ec0b78d 100644
--- a/spec/services/namespaces/projects/assign_runtimes_service_spec.rb
+++ b/spec/services/namespaces/projects/assign_runtimes_service_spec.rb
@@ -57,9 +57,27 @@
           target_type: 'NamespaceProject'
         )
       end
+
+      it 'queues job to update runtimes' do
+        allow(UpdateRuntimeCompatibilityJob).to receive(:perform_later)
+
+        service_response
+
+        expect(UpdateRuntimeCompatibilityJob).to have_received(:perform_later).with(
+          { namespace_project_id: project.id }
+        )
+      end
+
+      it { expect { service_response }.to change { project.reload.primary_runtime }.to(runtimes.first) }
+
+      context 'when adding multiple runtimes' do
+        let(:runtimes) { 2.times.map { create(:runtime, namespace: project.namespace) } }
+
+        it { expect { service_response }.not_to change { project.reload.primary_runtime } }
+      end
     end
 
-    context 'when removing a project' do
+    context 'when removing a runtime' do
       let(:runtime) { create(:runtime, namespace: project.namespace) }
       let!(:namespace_project_runtime_assignment) do
         create(:namespace_project_runtime_assignment, namespace_project: project, runtime: runtime)
@@ -88,9 +106,19 @@
           target_type: 'NamespaceProject'
         )
       end
+
+      it 'queues job to update runtimes' do
+        allow(UpdateRuntimeCompatibilityJob).to receive(:perform_later)
+
+        service_response
+
+        expect(UpdateRuntimeCompatibilityJob).to have_received(:perform_later).with(
+          { namespace_project_id: project.id }
+        )
+      end
     end
 
-    context 'when adding and removing a project' do
+    context 'when adding and removing a runtime' do
       let(:runtime) { create(:runtime, namespace: project.namespace) }
       let!(:namespace_project_runtime_assignment) do
         create(:namespace_project_runtime_assignment, namespace_project: project, runtime: runtime)
@@ -119,6 +147,16 @@
           target_type: 'NamespaceProject'
         )
       end
+
+      it 'queues job to update runtimes' do
+        allow(UpdateRuntimeCompatibilityJob).to receive(:perform_later)
+
+        service_response
+
+        expect(UpdateRuntimeCompatibilityJob).to have_received(:perform_later).with(
+          { namespace_project_id: project.id }
+        )
+      end
     end
   end
 end
diff --git a/spec/services/namespaces/projects/update_service_spec.rb b/spec/services/namespaces/projects/update_service_spec.rb
index 119ffa4f..5d25904e 100644
--- a/spec/services/namespaces/projects/update_service_spec.rb
+++ b/spec/services/namespaces/projects/update_service_spec.rb
@@ -70,5 +70,27 @@
         target_type: 'NamespaceProject'
       )
     end
+
+    it 'queues job to update runtimes' do
+      allow(UpdateRuntimeCompatibilityJob).to receive(:perform_later)
+
+      service_response
+
+      expect(UpdateRuntimeCompatibilityJob).to have_received(:perform_later).with(
+        { namespace_project_id: namespace_project.id }
+      )
+    end
+
+    context 'without changing the primary runtime' do
+      let(:params) { { name: namespace_project_name } }
+
+      it 'does not queue job to update runtimes' do
+        allow(UpdateRuntimeCompatibilityJob).to receive(:perform_later)
+
+        service_response
+
+        expect(UpdateRuntimeCompatibilityJob).not_to have_received(:perform_later)
+      end
+    end
   end
 end