diff --git a/test/sink/nighthawk_sink_client_test.cc b/test/sink/nighthawk_sink_client_test.cc
index 8a14f006a..f490f886a 100644
--- a/test/sink/nighthawk_sink_client_test.cc
+++ b/test/sink/nighthawk_sink_client_test.cc
@@ -1,5 +1,6 @@
 #include "external/envoy/source/common/protobuf/protobuf.h"
 
+#include "api/client/output.pb.h"
 #include "api/sink/sink.grpc.pb.h"
 #include "api/sink/sink_mock.grpc.pb.h"