diff --git a/src/openvpn/tun.c b/src/openvpn/tun.c
index 1f0eadd..0832375 100644
--- a/src/openvpn/tun.c
+++ b/src/openvpn/tun.c
@@ -1822,7 +1822,7 @@
     }
 }
 
-int
+static int
 write_tun_header(struct tuntap *tt, uint8_t *buf, int len)
 {
     if (tt->type == DEV_TYPE_TUN)
@@ -1855,7 +1855,7 @@
     }
 }
 
-int
+static int
 read_tun_header(struct tuntap *tt, uint8_t *buf, int len)
 {
     if (tt->type == DEV_TYPE_TUN)