diff --git a/sys/net/gnrc/transport_layer/tcp/gnrc_tcp_eventloop.c b/sys/net/gnrc/transport_layer/tcp/gnrc_tcp_eventloop.c
index e73f1f78d170..0261d6cc3557 100644
--- a/sys/net/gnrc/transport_layer/tcp/gnrc_tcp_eventloop.c
+++ b/sys/net/gnrc/transport_layer/tcp/gnrc_tcp_eventloop.c
@@ -162,6 +162,7 @@ static int _receive(gnrc_pktsnip_t *pkt)
             return -ENOMSG;
         }
         pkt->type = GNRC_NETTYPE_UNDEF;
+        hdr = (tcp_hdr_t *)tcp->data;
     }
 
     /* Validate checksum */