diff --git a/src/openvpn/tun.c b/src/openvpn/tun.c
index 9b830285..80eaa2c4 100644
--- a/src/openvpn/tun.c
+++ b/src/openvpn/tun.c
@@ -5374,6 +5374,7 @@ netsh_enable_dhcp(const char *actual_name)
 static bool
 service_enable_dhcp(const struct tuntap *tt)
 {
+    DWORD len;
     bool ret = false;
     ack_message_t ack;
     struct gc_arena gc = gc_new();