diff --git a/src/include/lwip/opt.h b/src/include/lwip/opt.h
index a6b50daa..8dcf0aa5 100644
--- a/src/include/lwip/opt.h
+++ b/src/include/lwip/opt.h
@@ -1545,7 +1545,7 @@
  * TCP_MSS, IP header, and link header.
  */
 #if !defined PBUF_POOL_BUFSIZE || defined __DOXYGEN__
-#define PBUF_POOL_BUFSIZE               LWIP_MEM_ALIGN_SIZE(TCP_MSS+40+PBUF_LINK_ENCAPSULATION_HLEN+PBUF_LINK_HLEN)
+#define PBUF_POOL_BUFSIZE               LWIP_MEM_ALIGN_SIZE(TCP_MSS+PBUF_IP_HLEN+PBUF_TRANSPORT_HLEN+PBUF_LINK_ENCAPSULATION_HLEN+PBUF_LINK_HLEN)
 #endif
 
 /**