diff --git a/module/ice-9/boot-9.scm b/module/ice-9/boot-9.scm
index d4a7d2327..a46145ed5 100644
--- a/module/ice-9/boot-9.scm
+++ b/module/ice-9/boot-9.scm
@@ -2060,16 +2060,6 @@ non-locally, that exit determines the continuation."
 ;;; {Load Paths}
 ;;;
 
-(eval-when (eval)
-  (define (compile-time-file-name-convention)
-    (let ((target ((@ (system base target) target-type))))
-      (cond ((equal? target %host-type)
-             (system-file-name-convention))
-            ((string-contains-ci target "mingw")
-             'windows)
-            (else
-             'posix)))))
-
 (let-syntax ((compile-time-case
               (lambda (stx)
                 (syntax-case stx ()
@@ -2087,9 +2077,7 @@ non-locally, that exit determines the continuation."
                               #'(begin form ...)
                               (next-clause #'(clauses ...))))))))))))
   ;; emacs: (put 'compile-time-case 'scheme-indent-function 1)
-  (compile-time-case (or (and (defined? 'compile-time-file-name-convention)
-                              (compile-time-file-name-convention))
-                         'posix)
+  (compile-time-case (system-file-name-convention)
     ((posix)
      (define (file-name-separator? c)
        (char=? c #\/))