wip
diff --git a/test/cpp/interop/server_helper.h b/test/cpp/interop/server_helper.h
index d738d05..006a0e3 100644
--- a/test/cpp/interop/server_helper.h
+++ b/test/cpp/interop/server_helper.h
@@ -36,6 +36,7 @@
 
 #include <memory>
 
+#include <grpc/compression.h>
 #include <grpc++/server_context.h>
 #include <grpc++/server_credentials.h>
 
@@ -49,6 +50,7 @@
   InteropContextInspector(const ::grpc::ServerContext& context);
 
   // Inspector methods, able to peek inside ServerContext go here.
+  grpc_compression_algorithm GetCallCompressionAlgorithm() const;
 
  private:
   const ::grpc::ServerContext& context_;