diff --git a/src/proto/os_unix.pro b/src/proto/os_unix.pro
index a8e961b..f30b78d 100644
--- a/src/proto/os_unix.pro
+++ b/src/proto/os_unix.pro
@@ -87,6 +87,6 @@
 void xsmp_init(void);
 void xsmp_close(void);
 void stop_timeout(void);
-volatile int *start_timeout(long msec);
+volatile sig_atomic_t *start_timeout(long msec);
 void delete_timer(void);
 /* vim: set ft=c : */