diff --git a/src/proto/os_win32.pro b/src/proto/os_win32.pro
index 7cdd156..b3acb4f 100644
--- a/src/proto/os_win32.pro
+++ b/src/proto/os_win32.pro
@@ -21,6 +21,7 @@
 void mch_hide __ARGS((char_u *name));
 int mch_ishidden __ARGS((char_u *name));
 int mch_isdir __ARGS((char_u *name));
+int mch_isrealdir __ARGS((char_u *name));
 int mch_mkdir __ARGS((char_u *name));
 int mch_rmdir __ARGS((char_u *name));
 int mch_is_hard_link __ARGS((char_u *fname));