diff --git a/bufferevent_ratelim.c b/bufferevent_ratelim.c
index d32f63b3..afae2e3a 100644
--- a/bufferevent_ratelim.c
+++ b/bufferevent_ratelim.c
@@ -245,6 +245,8 @@ _bufferevent_get_rlim_max(struct bufferevent_private *bev, int is_write)
 		CLAMPTO(share);
 	}
 
+	if (max_so_far < 0)
+		max_so_far = 0;
 	return max_so_far;
 }