diff --git a/test/cpp/end2end/async_end2end_test.cc b/test/cpp/end2end/async_end2end_test.cc
index 74290c3..364aa41 100644
--- a/test/cpp/end2end/async_end2end_test.cc
+++ b/test/cpp/end2end/async_end2end_test.cc
@@ -179,6 +179,17 @@
   void SetUp() GRPC_OVERRIDE {
     int port = grpc_pick_unused_port_or_die();
     server_address_ << "localhost:" << port;
+
+    // It is currently unsupported to mix sync and async services
+    // in the same server, so first test that (for coverage)
+    ServerBuilder build_bad;
+    build_bad.AddListeningPort(server_address_.str(),
+				grpc::InsecureServerCredentials());
+    build_bad.RegisterAsyncService(&service_);
+    grpc::cpp::test::util::TestService::Service sync_service;
+    build_bad.RegisterService(&sync_service);
+    GPR_ASSERT(build_bad.BuildAndStart() == nullptr);
+
     // Setup server
     ServerBuilder builder;
     builder.AddListeningPort(server_address_.str(),