diff --git a/lib/gitlab/ci/config/entry/image.rb b/lib/gitlab/ci/config/entry/image.rb
index 0beeb44c272..21c42857895 100644
--- a/lib/gitlab/ci/config/entry/image.rb
+++ b/lib/gitlab/ci/config/entry/image.rb
@@ -24,7 +24,7 @@ module Gitlab
           end
 
           entry :ports, Entry::Ports,
-            description: 'Ports used expose the image'
+            description: 'Ports used to expose the image'
 
           attributes :ports
 
diff --git a/lib/gitlab/ci/config/entry/service.rb b/lib/gitlab/ci/config/entry/service.rb
index 084fa4047a4..8d16371e857 100644
--- a/lib/gitlab/ci/config/entry/service.rb
+++ b/lib/gitlab/ci/config/entry/service.rb
@@ -24,6 +24,9 @@ module Gitlab
             validates :alias, type: String, presence: true, unless: ->(record) { record.ports.blank? }
           end
 
+          entry :ports, Entry::Ports,
+            description: 'Ports used to expose the service'
+
           def alias
             value[:alias]
           end
diff --git a/spec/lib/gitlab/ci/config/entry/service_spec.rb b/spec/lib/gitlab/ci/config/entry/service_spec.rb
index d5bd139b5f1..d31866a1987 100644
--- a/spec/lib/gitlab/ci/config/entry/service_spec.rb
+++ b/spec/lib/gitlab/ci/config/entry/service_spec.rb
@@ -112,6 +112,16 @@ describe Gitlab::Ci::Config::Entry::Service do
           it 'is valid' do
             expect(entry).to be_valid
           end
+
+          context 'when unknown port keys detected' do
+            let(:ports) { [{ number: 80, invalid_key: 'foo' }] }
+
+            it 'is not valid' do
+              expect(entry).not_to be_valid
+              expect(entry.errors.first)
+                .to match /port config contains unknown keys: invalid_key/
+            end
+          end
         end
 
         describe '#ports' do