diff --git a/src/buf/buf_impl.rs b/src/buf/buf_impl.rs
index 9367eb2df..38ecf4bd9 100644
--- a/src/buf/buf_impl.rs
+++ b/src/buf/buf_impl.rs
@@ -1120,6 +1120,10 @@ pub trait Buf {
     /// let bytes = (&b"hello world"[..]).copy_to_bytes(5);
     /// assert_eq!(&bytes[..], &b"hello"[..]);
     /// ```
+    ///
+    /// # Panics
+    ///
+    /// This function panics if `len > self.remaining()`.
     fn copy_to_bytes(&mut self, len: usize) -> crate::Bytes {
         use super::BufMut;