diff --git a/gash/word.scm b/gash/word.scm
index 26127ae..a06f87b 100644
--- a/gash/word.scm
+++ b/gash/word.scm
@@ -99,7 +99,7 @@ in the string @var{ifs}."
     (string->char-set ifs))
 
   (define char-set:ifs/nw
-    (char-set-difference char-set:ifs char-set:whitespace))
+    (string->char-set (string-delete char-set:whitespace ifs)))
 
   (define (wedge-apart-quote qword)
     (let loop ((qword (normalize-word qword)) (acc '()))