diff --git a/quiche/http2/adapter/adapter_impl_comparison_test.cc b/quiche/http2/adapter/adapter_impl_comparison_test.cc
index df0d21b45..bc56a8009 100644
--- a/quiche/http2/adapter/adapter_impl_comparison_test.cc
+++ b/quiche/http2/adapter/adapter_impl_comparison_test.cc
@@ -44,6 +44,7 @@ class ComparisonTest : public ::quiche::test::QuicheTest {
         options.perspective = p;
         return OgHttp2Adapter::Create(visitor, options);
     }
+    return nullptr;  // Unreachable unless enum is corrupted.
   }
 };