diff --git a/gitnexus/test/unit/registry-primary-flag.test.ts b/gitnexus/test/unit/registry-primary-flag.test.ts
index 759114af5..7e428e031 100644
--- a/gitnexus/test/unit/registry-primary-flag.test.ts
+++ b/gitnexus/test/unit/registry-primary-flag.test.ts
@@ -148,15 +148,20 @@ describe('primaryLanguages', () => {
   });
 
   it('returns exactly the flipped languages (env opts in unmigrated, opts out migrated)', () => {
-    // Python is migrated (default-on), explicitly off via env var.
-    // Go and Java are unmigrated (default-off); Go opted in, Java left off.
+    // Python and C# are migrated (default-on); both explicitly off via
+    // env vars. Go and Java are unmigrated (default-off); Go opted in,
+    // Java left off. This pins the semantics across all
+    // MIGRATED_LANGUAGES — as languages migrate, add their
+    // `REGISTRY_PRIMARY_<LANG> = 'false'` line here alongside Python / C#.
     process.env['REGISTRY_PRIMARY_PYTHON'] = 'false';
+    process.env['REGISTRY_PRIMARY_CSHARP'] = 'false';
     process.env['REGISTRY_PRIMARY_GO'] = '1';
     const enabled = primaryLanguages();
     expect(enabled.has(SupportedLanguages.Python)).toBe(false);
+    expect(enabled.has(SupportedLanguages.CSharp)).toBe(false);
     expect(enabled.has(SupportedLanguages.Go)).toBe(true);
     expect(enabled.has(SupportedLanguages.Java)).toBe(false);
-    // Only Go is on: migrated-default-Python overridden off, Go explicitly on.
+    // Only Go is on: migrated defaults overridden off, Go explicitly on.
     expect(enabled.size).toBe(1);
   });