diff --git a/src/core/tcp_out.c b/src/core/tcp_out.c
index c40e5af8..64579ee5 100644
--- a/src/core/tcp_out.c
+++ b/src/core/tcp_out.c
@@ -1040,12 +1040,12 @@ tcp_enqueue_flags(struct tcp_pcb *pcb, u8_t flags)
   u8_t optflags = 0;
   u8_t optlen = 0;
 
-  LWIP_DEBUGF(TCP_QLEN_DEBUG, ("tcp_enqueue_flags: queuelen: %"U16_F"\n", (u16_t)pcb->snd_queuelen));
-
   LWIP_ASSERT("tcp_enqueue_flags: need either TCP_SYN or TCP_FIN in flags (programmer violates API)",
               (flags & (TCP_SYN | TCP_FIN)) != 0);
   LWIP_ASSERT("tcp_enqueue_flags: invalid pcb", pcb != NULL);
 
+  LWIP_DEBUGF(TCP_QLEN_DEBUG, ("tcp_enqueue_flags: queuelen: %"U16_F"\n", (u16_t)pcb->snd_queuelen));
+
   /* No need to check pcb->snd_queuelen if only SYN or FIN are allowed! */
 
   /* Get options for this segment. This is a special case since this is the