diff --git a/src/proto/os_unix.pro b/src/proto/os_unix.pro
index 89dff77..be6eb6f 100644
--- a/src/proto/os_unix.pro
+++ b/src/proto/os_unix.pro
@@ -41,6 +41,7 @@
 void mch_free_acl __ARGS((vim_acl_T aclent));
 void mch_hide __ARGS((char_u *name));
 int mch_isdir __ARGS((char_u *name));
+int mch_isrealdir __ARGS((char_u *name));
 int mch_can_exe __ARGS((char_u *name, char_u **path, int use_path));
 int mch_nodetype __ARGS((char_u *name));
 void mch_early_init __ARGS((void));