diff --git a/m4/check-libc.m4 b/m4/check-libc.m4
index f726a43..a4df0b7 100644
--- a/m4/check-libc.m4
+++ b/m4/check-libc.m4
@@ -22,7 +22,6 @@ AC_CACHE_CHECK([for getpagesize], ac_cv_func_getpagesize, [
 AM_CONDITIONAL([HAVE_ASPRINTF], [test "x$ac_cv_func_asprintf" = xyes])
 AM_CONDITIONAL([HAVE_FREEZERO], [test "x$ac_cv_func_freezero" = xyes])
 AM_CONDITIONAL([HAVE_GETPAGESIZE], [test "x$ac_cv_func_getpagesize" = xyes])
-AM_CONDITIONAL([HAVE_TIMESPECSUB], [test "x$ac_cv_func_timespecsub" = xyes])
 AM_CONDITIONAL([HAVE_MEMMEM], [test "x$ac_cv_func_memmem" = xyes])
 AM_CONDITIONAL([HAVE_READPASSPHRASE], [test "x$ac_cv_func_readpassphrase" = xyes])
 AM_CONDITIONAL([HAVE_REALLOCARRAY], [test "x$ac_cv_func_reallocarray" = xyes])