diff --git a/man2/sendfile.2 b/man2/sendfile.2
index 9e6ae3c0b..878c1edef 100644
--- a/man2/sendfile.2
+++ b/man2/sendfile.2
@@ -109,6 +109,11 @@ changes the file offset appropriately.
 If the transfer was successful, the number of bytes written to
 .I out_fd
 is returned.
+Note that a successful call to
+.BR sendfile ()
+may write fewer bytes than requested;
+the caller should be prepared to retry the call if there were unsent bytes.
+
 On error, \-1 is returned, and
 .I errno
 is set appropriately.