diff --git a/include/rocksdb/rate_limiter.h b/include/rocksdb/rate_limiter.h
index a6c606e4c..df0b4e23d 100644
--- a/include/rocksdb/rate_limiter.h
+++ b/include/rocksdb/rate_limiter.h
@@ -59,13 +59,15 @@ class RateLimiter : public Customizable {
   // Request for token for bytes. If this request can not be satisfied, the call
   // is blocked. Caller is responsible to make sure
   // bytes <= GetSingleBurstBytes()
+  // and bytes >= 0.
   virtual void Request(const int64_t /*bytes*/, const Env::IOPriority /*pri*/) {
     assert(false);
   }
 
   // Request for token for bytes and potentially update statistics. If this
   // request can not be satisfied, the call is blocked. Caller is responsible to
-  // make sure bytes <= GetSingleBurstBytes().
+  // make sure bytes <= GetSingleBurstBytes()
+  // and bytes >= 0.
   virtual void Request(const int64_t bytes, const Env::IOPriority pri,
                        Statistics* /* stats */) {
     // For API compatibility, default implementation calls the older API in