diff --git a/conformance/conformance_cpp.cc b/conformance/conformance_cpp.cc
index 3470eebc1e..dd753ca820 100644
--- a/conformance/conformance_cpp.cc
+++ b/conformance/conformance_cpp.cc
@@ -232,7 +232,7 @@ util::StatusOr<bool> Harness::ServeConformanceRequest() {
 
   std::string serialized_input;
   serialized_input.resize(in_len);
-  RETURN_IF_ERROR(ReadFd(STDIN_FILENO, const_cast<char*>(serialized_input.data()), in_len));
+  RETURN_IF_ERROR(ReadFd(STDIN_FILENO, &serialized_input[0], in_len));
 
   ConformanceRequest request;
   GOOGLE_CHECK(request.ParseFromString(serialized_input));