diff --git a/basis/io/streams/byte-array/fast/fast.factor b/basis/io/streams/byte-array/fast/fast.factor
index 2948e2bc61..9f74d0778b 100644
--- a/basis/io/streams/byte-array/fast/fast.factor
+++ b/basis/io/streams/byte-array/fast/fast.factor
@@ -1,6 +1,7 @@
 ! Copyright (C) 2010 Slava Pestov.
 ! See http://factorcode.org/license.txt for BSD license.
-USING: alien byte-vectors io kernel libc math sequences ;
+USING: alien byte-arrays byte-vectors io kernel libc math
+sequences ;
 IN: io.streams.byte-array.fast
 
 ! This is split off from io.streams.byte-array because it uses
@@ -8,6 +9,10 @@ IN: io.streams.byte-array.fast
 ! optimizing compiler has been loaded.
 
 M: byte-vector stream-write
-    [ dup byte-length tail-slice swap ]
-    [ [ [ byte-length ] bi@ + ] keep lengthen ] 2bi
-    dup byte-length memcpy ;
+    over byte-array? [
+        push-all ! faster than memcpy
+    ] [
+        2dup [ byte-length ] bi@
+        3dup + swap lengthen
+        [ tail-slice swap ] curry dip memcpy
+    ] if ;