diff --git a/include/ucore/rate_limit.h b/include/ucore/rate_limit.h
index c5f8d9a..10bd00f 100644
--- a/include/ucore/rate_limit.h
+++ b/include/ucore/rate_limit.h
@@ -34,7 +34,7 @@
  *
  * uc_ratelimit_init(&r,20, 1, time(NULL));
  *
- * NOTE. period * tickets * tickets must not exceed the value of a long
+ * NOTE. 2 * (period + 1) * tickets * tickets must not exceed the range of the RateLimit.funds
  *
  * for (;;) {
  *    int fd = accept(..);
@@ -67,7 +67,7 @@ struct RateLimit {
  * Initialize a struct RateLimit, which can hand out @tickets per @period
  * the perioid must be in the same units as the current_ts
  * 
- * NOTE. period * tickets * tickets must not exceed the range of the RateLimit.funds
+ * NOTE. 2 * (period + 1) * tickets * tickets must not exceed the range of the RateLimit.funds
  *
  * @param r RateLimit to initialize
  * @param tickets number of tickets (bucket depth)