diff --git a/test/cpp/microbenchmarks/bm_chttp2_hpack.cc b/test/cpp/microbenchmarks/bm_chttp2_hpack.cc
index 8fbfd0fa132bf3c60a78d8fdf5c7101a55a59918..55d2d2f58d010f6933a90a1aff6f8a2f513bee14 100644
--- a/test/cpp/microbenchmarks/bm_chttp2_hpack.cc
+++ b/test/cpp/microbenchmarks/bm_chttp2_hpack.cc
@@ -97,7 +97,7 @@ static void BM_HpackEncoderEncodeHeader(benchmark::State &state) {
       logged_representative_output = true;
       for (size_t i = 0; i < outbuf.count; i++) {
         char *s = grpc_dump_slice(outbuf.slices[i], GPR_DUMP_HEX);
-        gpr_log(GPR_DEBUG, "%" PRId64 ": %s", i, s);
+        gpr_log(GPR_DEBUG, "%" PRIdPTR ": %s", i, s);
         gpr_free(s);
       }
     }