diff --git a/src/core/lib/transport/metadata_batch.cc b/src/core/lib/transport/metadata_batch.cc
index 15a75f83fce..14fde0ffc14 100644
--- a/src/core/lib/transport/metadata_batch.cc
+++ b/src/core/lib/transport/metadata_batch.cc
@@ -276,6 +276,7 @@ std::string GrpcStreamNetworkState::DisplayValue(ValueType x) {
     case kNotSeenByServer:
       return "not seen by server";
   }
+  GPR_UNREACHABLE_CODE(return "unknown value");
 }
 
 std::string PeerString::DisplayValue(ValueType x) { return std::string(x); }