diff --git a/sys/net/gnrc/network_layer/ipv6/gnrc_ipv6.c b/sys/net/gnrc/network_layer/ipv6/gnrc_ipv6.c
index 575d603cdf..9e1bd1b159 100644
--- a/sys/net/gnrc/network_layer/ipv6/gnrc_ipv6.c
+++ b/sys/net/gnrc/network_layer/ipv6/gnrc_ipv6.c
@@ -382,7 +382,7 @@ static int _fill_ipv6_hdr(gnrc_netif_t *netif, gnrc_pktsnip_t *ipv6)
         int idx;
 
         gnrc_netif_acquire(netif);
-        invalid_src = ((idx = gnrc_netif_ipv6_addr_idx(netif, &hdr->src)) == -1) ||
+        invalid_src = ((idx = gnrc_netif_ipv6_addr_idx(netif, &hdr->src)) >= 0) &&
             (gnrc_netif_ipv6_addr_get_state(netif, idx) != GNRC_NETIF_IPV6_ADDRS_FLAGS_STATE_VALID);
         gnrc_netif_release(netif);
         if (invalid_src) {