diff --git a/src/edit.c b/src/edit.c
index 25d4b58..7028dd3 100644
--- a/src/edit.c
+++ b/src/edit.c
@@ -2683,7 +2683,7 @@
     args[1] = base;
     args[2] = colbuf;
     args[3] = (char_u *)(preproc ? "1" : "0");
-    return call_vim_function(curbuf->b_p_cfu, 4, args, FALSE);
+    return (char_u *)call_func_retstr(curbuf->b_p_cfu, 4, args, FALSE);
 }
 
 /*