fix compiling error
diff --git a/test/cpp/end2end/end2end_test.cc b/test/cpp/end2end/end2end_test.cc
index 40ba0c0..e3408bf 100644
--- a/test/cpp/end2end/end2end_test.cc
+++ b/test/cpp/end2end/end2end_test.cc
@@ -995,7 +995,7 @@
Status s = stub_->Echo(&context, request, &response);
EXPECT_FALSE(s.ok());
auto trailers = context.GetServerTrailingMetadata();
- EXPECT_EQ(1, trailers.count(kDebugInfoTrailerKey));
+ EXPECT_EQ(1u, trailers.count(kDebugInfoTrailerKey));
auto iter = trailers.find(kDebugInfoTrailerKey);
EXPECT_EQ(expected_string, iter->second);
// Parse the returned trailer into a DebugInfo proto.