diff --git a/pkg/lwip/contrib/sock/ip/lwip_sock_ip.c b/pkg/lwip/contrib/sock/ip/lwip_sock_ip.c
index e76b19bcc6..43dd2f266a 100644
--- a/pkg/lwip/contrib/sock/ip/lwip_sock_ip.c
+++ b/pkg/lwip/contrib/sock/ip/lwip_sock_ip.c
@@ -45,6 +45,7 @@ int sock_ip_create(sock_ip_t *sock, const sock_ip_ep_t *local,
                                 NETCONN_RAW)) == 0) {
         sock->base.conn = tmp;
 #if IS_ACTIVE(SOCK_HAS_ASYNC)
+        sock->base.async_cb.gen = NULL;
         netconn_set_callback_arg(sock->base.conn, &sock->base);
 #endif
     }
diff --git a/pkg/lwip/contrib/sock/udp/lwip_sock_udp.c b/pkg/lwip/contrib/sock/udp/lwip_sock_udp.c
index 7dead578f8..363c6c6d30 100644
--- a/pkg/lwip/contrib/sock/udp/lwip_sock_udp.c
+++ b/pkg/lwip/contrib/sock/udp/lwip_sock_udp.c
@@ -41,6 +41,7 @@ int sock_udp_create(sock_udp_t *sock, const sock_udp_ep_t *local,
                                 NETCONN_UDP)) == 0) {
         sock->base.conn = tmp;
 #if IS_ACTIVE(SOCK_HAS_ASYNC)
+        sock->base.async_cb.gen = NULL;
         netconn_set_callback_arg(sock->base.conn, &sock->base);
 #endif
     }