Restricted the check to GUNC
diff --git a/src/core/lib/support/log_linux.c b/src/core/lib/support/log_linux.c
index ca04c02..508fae4 100644
--- a/src/core/lib/support/log_linux.c
+++ b/src/core/lib/support/log_linux.c
@@ -95,9 +95,9 @@
     strcpy(time_buffer, "error:strftime");
   }
 
-  gpr_asprintf(&prefix, "%s%s.%09d %7tu %s:%d]",
+  gpr_asprintf(&prefix, "%s%s.%09" PRId32 " %7ld %s:%d]",
                gpr_log_severity_string(args->severity), time_buffer,
-               (int)(now.tv_nsec), gettid(), display_file, args->line);
+               now.tv_nsec, gettid(), display_file, args->line);
 
   fprintf(stderr, "%-60s %s\n", prefix, args->message);
   gpr_free(prefix);