diff --git a/src/cpp/server/server.cc b/src/cpp/server/server.cc
index dfc2b303bca..29db0b41c3b 100644
--- a/src/cpp/server/server.cc
+++ b/src/cpp/server/server.cc
@@ -329,6 +329,15 @@ bool Server::Start(ServerCompletionQueue** cqs, size_t num_cqs) {
   grpc_server_start(server_);
 
   if (!has_generic_service_) {
+    if (!sync_methods_->empty()) {
+      unknown_method_.reset(new RpcServiceMethod(
+          "unknown", RpcMethod::BIDI_STREAMING, new UnknownMethodHandler));
+      // Use of emplace_back with just constructor arguments is not accepted
+      // here
+      // by gcc-4.4 because it can't match the anonymous nullptr with a proper
+      // constructor implicitly. Construct the object and use push_back.
+      sync_methods_->push_back(SyncRequest(unknown_method_.get(), nullptr));
+    }
     for (size_t i = 0; i < num_cqs; i++) {
       new UnimplementedAsyncRequest(this, cqs[i]);
     }