diff --git a/ssh-agent.c b/ssh-agent.c
index 30d99b9..7bfa290 100644
--- a/ssh-agent.c
+++ b/ssh-agent.c
@@ -507,6 +507,7 @@
 	struct sockaddr_un sunaddr;
 	pid_t pid;
 	char *shell, *format, *pidstr, pidstrbuf[1 + 3 * sizeof pid];
+	extern int optind;
 
 	/* check if RSA support exists */
 	if (rsa_alive() == 0) {