diff --git a/lisp/erk.el b/lisp/erk.el
index 27bbf64..759194a 100644
--- a/lisp/erk.el
+++ b/lisp/erk.el
@@ -78,7 +78,7 @@ to clone from within the fork."
 
 (defcustom erk-replace-package-prefix
   (lm-with-file (buffer-file-name)
-    (car (string-split (lm-get-package-name) "\\.")))
+    (car (split-string (lm-get-package-name) "\\.")))
   "The prefix is used to features and file names."
   :group 'erk
   :type 'string)