qsort_r appeared in glibc 2.8
diff --git a/src/util.c b/src/util.c
index a6f87a0..da15a03 100644
--- a/src/util.c
+++ b/src/util.c
@@ -686,7 +686,8 @@ void git__qsort_r(
void *els, size_t nel, size_t elsize, git__sort_r_cmp cmp, void *payload)
{
#if defined(__MINGW32__) || defined(__OpenBSD__) || defined(AMIGA) || \
- defined(__gnu_hurd__)
+ defined(__gnu_hurd__) || \
+ (__GLIBC__ == 2 && __GLIBC_MINOR__ < 8)
git__insertsort_r(els, nel, elsize, NULL, cmp, payload);
#elif defined(GIT_WIN32)
git__qsort_r_glue glue = { cmp, payload };