diff --git a/slock.c b/slock.c
index d55eb3d..5ae738c 100644
--- a/slock.c
+++ b/slock.c
@@ -177,7 +177,7 @@ readpw(Display *dpy, struct xrandr *rr, struct lock **locks, int nscreens,
 				break;
 			case XK_BackSpace:
 				if (len)
-					passwd[len--] = '\0';
+					passwd[--len] = '\0';
 				break;
 			default:
 				if (num && !iscntrl((int)buf[0]) &&