diff --git a/include/net/pkt_sched.h b/include/net/pkt_sched.h
index 87496e3..7352e45 100644
--- a/include/net/pkt_sched.h
+++ b/include/net/pkt_sched.h
@@ -140,7 +140,7 @@
 	if (bound <= 1000000 || delta_sec > (0x7FFFFFFF/1000000)-1)
 		return bound;
 	delta = delta_sec * 1000000;
-	if (delta > bound)
+	if (delta > bound || delta < 0)
 		delta = bound;
 	return delta;
 }
@@ -156,7 +156,8 @@
 		   __delta += 1000000; \
 	   case 1: \
 		   __delta += 1000000; \
-	   case 0: ; \
+	   case 0: \
+		   __delta = abs(__delta); \
 	   } \
 	   __delta; \
 })