diff --git a/src/code/fd-stream.lisp b/src/code/fd-stream.lisp
index 80e294141a43569502b90aff7866f106c5f8a2c4..470dfe23e94422627320af48f101f342c630052a 100644
--- a/src/code/fd-stream.lisp
+++ b/src/code/fd-stream.lisp
@@ -1682,7 +1682,9 @@
 	   nil
 	   (values (truncate size (fd-stream-element-size stream))))))
     (:file-position
-     (fd-stream-file-position stream arg1))))
+     (fd-stream-file-position stream arg1))
+    (:clear-output
+     (setf (fd-stream-obuf-tail stream) 0))))
 
 
 ;;; FD-STREAM-FILE-POSITION -- internal.