diff --git a/extras/mini-os/lib/math.c b/extras/mini-os/lib/math.c
index b98cc1d..1b63a83 100644
--- a/extras/mini-os/lib/math.c
+++ b/extras/mini-os/lib/math.c
@@ -366,6 +366,14 @@ __divdi3(quad_t a, quad_t b)
 	return (neg ? -uq : uq);
 }
 
+quad_t
+__divmoddi4(quad_t a, quad_t b, quad_t *r)
+{
+	quad_t d = __divdi3(a, b);
+	*r = a - (d * b);
+	return d;
+}
+
 /*
  * From
  * udivdi3.c