diff --git a/trees/cb/cb.factor b/trees/cb/cb.factor
index fda8fc3..2147d92 100644
--- a/trees/cb/cb.factor
+++ b/trees/cb/cb.factor
@@ -14,10 +14,11 @@
 ! critical bit) in a length field (encoded as an integer and a mask) and two
 ! successor pointers. Arbitrary data objects make up its leaves.
 
-USING: accessors alien arrays assocs byte-arrays combinators.short-circuit fry
-io.binary io.encodings.binary io.encodings.private io.encodings.string
-io.encodings.utf8 kernel layouts locals make math math.private namespaces parser
-prettyprint.custom sequences serialize strings trees trees.private vectors ;
+USING: accessors alien arrays assocs byte-arrays combinators
+combinators.short-circuit fry io.binary io.encodings.binary io.encodings.private
+io.encodings.string io.encodings.utf8 kernel layouts locals make math
+math.private namespaces parser prettyprint.custom sequences serialize strings
+trees trees.private vectors ;
 IN: trees.cb
 
 TUPLE: cb < tree ;
@@ -53,17 +54,31 @@ TUPLE: cb-node { byte# integer } { bits integer } left right ;
     bitxor msb0
     [ key-side ] keep ;
 
+: elt-from-long-seq ( seq1 seq2 -- elt i/f )
+    2dup [ length ] bi@ {
+        { [ 2dup > ] [ 2nip [ swap nth ] keep ] }
+        { [ 2dup < ] [ drop [ drop ] 2dip [ swap nth ] keep ] }
+        [ 4drop 0 f ]
+    } cond ;
+
+: order-by-length ( seq1 seq2 -- seq-short seq-long )
+    2dup [ length ] bi@ > [ swap ] when ;
+
 ! For two byte strings, calculate the critical bit, byte and direction of
-! difference (0 = left, 1 = right).
-: bytes-diff ( newbytes oldbytes -- side bits byte# )
+! difference.
+: (bytes-diff) ( newbytes oldbytes -- side bits byte# )
     2dup mismatch
     [
         [ '[ _ swap nth ] bi@ byte-diff ] keep
     ] [
         ! Equal prefix over full (shorter) byte sequence.
+        elt-from-long-seq [ [ 0  ] dip ] [ ] if* ;
         [ 1 255 ] 2dip shorter length 1 -
     ] if* ;
 
+: bytes-diff ( newbytes oldbytes -- side bits byte#/f )
+    bytes-diff ;
+
 PRIVATE>
 
 GENERIC: key>bytes* ( key -- bytes )