diff --git a/src/include/unistd.h b/src/include/unistd.h
index 637b6c3a..ae4f7aa9 100644
--- a/src/include/unistd.h
+++ b/src/include/unistd.h
@@ -126,7 +126,7 @@ int	 getpagesize __P((void));
 char	*getpass __P((const char *));
 char	*getusershell __P((void));
 char	*getwd __P((char *));			/* obsoleted by getcwd() */
-int	 initgroups __P((const char *, int));
+int	 initgroups __P((const char *, gid_t));
 int	 iruserok __P((u_long, int, const char *, const char *));
 int	 mknod __P((const char *, mode_t, dev_t));
 int	 mkstemp __P((char *));