diff --git a/lib/sort.c b/lib/sort.c
index 9615678..6abbaf3 100644
--- a/lib/sort.c
+++ b/lib/sort.c
@@ -67,7 +67,7 @@
 	}
 
 	/* sort */
-	for (i = n - size; i >= 0; i -= size) {
+	for (i = n - size; i > 0; i -= size) {
 		swap(base, base + i, size);
 		for (r = 0; r * 2 + size < i; r = c) {
 			c = r * 2 + size;