diff --git a/src/os_unix.c b/src/os_unix.c
index cd3b68e..528089b 100644
--- a/src/os_unix.c
+++ b/src/os_unix.c
@@ -2397,7 +2397,7 @@
  * return TRUE if process "pid" is still running
  */
     int
-mch_process_running(pid_t pid)
+mch_process_running(long pid)
 {
     // EMX kill() not working correctly, it seems
     return kill(pid, 0) == 0;