diff --git a/src/core/tcp_in.c b/src/core/tcp_in.c
index c050a05a..eff719c6 100644
--- a/src/core/tcp_in.c
+++ b/src/core/tcp_in.c
@@ -758,7 +758,9 @@ tcp_receive(struct tcp_pcb *pcb)
 
       /* Update the send buffer space. */
       pcb->acked = ackno - pcb->lastack;
-      pcb->snd_buf += pcb->acked;
+
+      /* FIX: Data split over odd boundaries */
+      pcb->snd_buf += ((pcb->acked+1) & ~0x1); /* Even the send buffer */
 
       /* Reset the fast retransmit variables. */
       pcb->dupacks = 0;
diff --git a/src/core/tcp_out.c b/src/core/tcp_out.c
index 368032d3..de92fba1 100644
--- a/src/core/tcp_out.c
+++ b/src/core/tcp_out.c
@@ -337,7 +337,10 @@ tcp_enqueue(struct tcp_pcb *pcb, void *arg, u16_t len,
     ++len;
   }
   pcb->snd_lbb += len;
-  pcb->snd_buf -= len;
+
+  /* FIX: Data split over odd boundaries */
+  pcb->snd_buf -= ((len+1) & ~0x1); /* Even the send buffer */
+
   /* update number of segments on the queues */
   pcb->snd_queuelen = queuelen;
   LWIP_DEBUGF(TCP_QLEN_DEBUG, ("tcp_enqueue: %d (after enqueued)\n", pcb->snd_queuelen));