diff --git a/tokio-stream/src/stream_ext.rs b/tokio-stream/src/stream_ext.rs
index 6cea7b55d..52d32024f 100644
--- a/tokio-stream/src/stream_ext.rs
+++ b/tokio-stream/src/stream_ext.rs
@@ -982,6 +982,8 @@ pub trait StreamExt: Stream {
 
     /// Slows down a stream by enforcing a delay between items.
     ///
+    /// The underlying timer behind this utility has a granularity of one millisecond.
+    ///
     /// # Example
     ///
     /// Create a throttled stream.