diff --git a/builtin/get-tar-commit-id.c b/builtin/get-tar-commit-id.c
index 491af9202d..453a411f3c 100644
--- a/builtin/get-tar-commit-id.c
+++ b/builtin/get-tar-commit-id.c
@@ -32,7 +32,7 @@ int cmd_get_tar_commit_id(int argc, const char **argv, const char *prefix)
 		die_errno("git get-tar-commit-id: read error");
 	if (n != HEADERSIZE)
 		die_errno("git get-tar-commit-id: EOF before reading tar header");
-	if (header->typeflag[0] != 'g')
+	if (header->typeflag[0] != TYPEFLAG_GLOBAL_HEADER)
 		return 1;
 
 	len = strtol(content, &end, 10);