diff --git a/spec/lib/gitlab/path_regex_spec.rb b/spec/lib/gitlab/path_regex_spec.rb
index 8dabe5a756b9b96885d6bd843a9c48b89f1cf121..50b045c6aad47bdb388c08f34d7e31c01b5e7a5f 100644
--- a/spec/lib/gitlab/path_regex_spec.rb
+++ b/spec/lib/gitlab/path_regex_spec.rb
@@ -170,6 +170,11 @@ def failure_message(constant_name, migration_helper, missing_words: [], addition
       expect(described_class::TOP_LEVEL_ROUTES)
         .to contain_exactly(*top_level_words), failure_block
     end
+
+    # We ban new items in this list, see https://gitlab.com/gitlab-org/gitlab/-/issues/215362
+    it 'does not allow expansion' do
+      expect(described_class::TOP_LEVEL_ROUTES.size).to eq(41)
+    end
   end
 
   describe 'GROUP_ROUTES' do
@@ -184,6 +189,11 @@ def failure_message(constant_name, migration_helper, missing_words: [], addition
       expect(described_class::GROUP_ROUTES)
         .to contain_exactly(*paths_after_group_id), failure_block
     end
+
+    # We ban new items in this list, see https://gitlab.com/gitlab-org/gitlab/-/issues/215362
+    it 'does not allow expansion' do
+      expect(described_class::GROUP_ROUTES.size).to eq(1)
+    end
   end
 
   describe 'PROJECT_WILDCARD_ROUTES' do
@@ -195,6 +205,11 @@ def failure_message(constant_name, migration_helper, missing_words: [], addition
         end
       end
     end
+
+    # We ban new items in this list, see https://gitlab.com/gitlab-org/gitlab/-/issues/215362
+    it 'does not allow expansion' do
+      expect(described_class::PROJECT_WILDCARD_ROUTES.size).to eq(21)
+    end
   end
 
   describe '.root_namespace_route_regex' do