updated for version 7.0021
diff --git a/src/proto/os_unix.pro b/src/proto/os_unix.pro
index 9a3908b..6018c8f 100644
--- a/src/proto/os_unix.pro
+++ b/src/proto/os_unix.pro
@@ -11,6 +11,7 @@
 void mch_suspend __ARGS((void));
 void mch_init __ARGS((void));
 void reset_signals __ARGS((void));
+int handle_sighup __ARGS((int when));
 int mch_check_win __ARGS((int argc, char **argv));
 int mch_input_isatty __ARGS((void));
 int mch_can_restore_title __ARGS((void));