diff --git a/kernel/exit.c b/kernel/exit.c
index 8f6185e..fb8de6c 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -899,12 +899,9 @@
 {
 	static DEFINE_SPINLOCK(low_water_lock);
 	static int lowest_to_date = THREAD_SIZE;
-	unsigned long *n = end_of_stack(current);
 	unsigned long free;
 
-	while (*n == 0)
-		n++;
-	free = (unsigned long)n - (unsigned long)end_of_stack(current);
+	free = stack_not_used(current);
 
 	if (free >= lowest_to_date)
 		return;