diff --git a/collects/rnrs/programs-6.ss b/collects/rnrs/programs-6.ss
index d6942d42e9..fbc2554043 100644
--- a/collects/rnrs/programs-6.ss
+++ b/collects/rnrs/programs-6.ss
@@ -1,7 +1,9 @@
 #lang scheme/base
 
+(require scheme/mpair)
+
 (provide command-line exit)
 
 (define (command-line)
-  (cons (path->string (find-system-path 'run-file))
-        (vector->list (current-command-line-arguments))))
+  (mcons (path->string (find-system-path 'run-file))
+         (list->mlist (vector->list (current-command-line-arguments)))))