diff --git a/libraries/net/eth/lwip-eth/arch/lpc17_emac.c b/libraries/net/eth/lwip-eth/arch/lpc17_emac.c
index 243f9930a04..e082fd495fa 100644
--- a/libraries/net/eth/lwip-eth/arch/lpc17_emac.c
+++ b/libraries/net/eth/lwip-eth/arch/lpc17_emac.c
@@ -346,6 +346,7 @@ static struct pbuf *lpc_low_level_input(struct netif *netif)
 	struct lpc_enetdata *lpc_enetif = netif->state;
 	struct pbuf *p = NULL;
 	u32_t idx, length;
+	u16_t origLength;
 
 #ifdef LOCK_RX_THREAD
 #if NO_SYS == 0
@@ -428,6 +429,7 @@ static struct pbuf *lpc_low_level_input(struct netif *netif)
 
 			/* Zero-copy */
 			p = lpc_enetif->rxb[idx];
+			origLength = p->len;
 			p->len = (u16_t) length;
 
 			/* Free pbuf from descriptor */
@@ -440,6 +442,7 @@ static struct pbuf *lpc_low_level_input(struct netif *netif)
     			LINK_STATS_INC(link.drop);
 
     			/* Re-queue the pbuf for receive */
+    			p->len = origLength;
     			lpc_rxqueue_pbuf(lpc_enetif, p);
 
     			LWIP_DEBUGF(UDP_LPC_EMAC | LWIP_DBG_TRACE,
@@ -809,9 +812,8 @@ static void packet_rx(void* pvParameters) {
         /* Wait for receive task to wakeup */
         sys_arch_sem_wait(&lpc_enetif->RxSem, 0);
 
-        /* Process packets until all empty */
-        while (LPC_EMAC->RxConsumeIndex != LPC_EMAC->RxProduceIndex)
-            lpc_enetif_input(lpc_enetif->netif);
+        /* Process packet for this semaphore signal */
+        lpc_enetif_input(lpc_enetif->netif);
     }
 }
 
diff --git a/libraries/net/lwip/lwip/core/pbuf.c b/libraries/net/lwip/lwip/core/pbuf.c
index 818eb620356..cd37c797237 100644
--- a/libraries/net/lwip/lwip/core/pbuf.c
+++ b/libraries/net/lwip/lwip/core/pbuf.c
@@ -998,6 +998,8 @@ pbuf_coalesce(struct pbuf *p, pbuf_layer layer)
   }
   err = pbuf_copy(q, p);
   LWIP_ASSERT("pbuf_copy failed", err == ERR_OK);
+  /* next line references err variable even if LWIP_ASSERT is ignored. */
+  (void)err;
   pbuf_free(p);
   return q;
 }
diff --git a/libraries/net/lwip/lwip/lwipopts.h b/libraries/net/lwip/lwip/lwipopts.h
index 10846e24169..4d07680dbcf 100644
--- a/libraries/net/lwip/lwip/lwipopts.h
+++ b/libraries/net/lwip/lwip/lwipopts.h
@@ -27,6 +27,8 @@
 #if NO_SYS == 0
 #include "cmsis_os.h"
 
+#define SYS_LIGHTWEIGHT_PROT        1
+
 #define LWIP_RAW                    0
 
 #define TCPIP_MBOX_SIZE             8
@@ -99,6 +101,7 @@
 #define MEMP_OVERFLOW_CHECK         1
 #define MEMP_SANITY_CHECK           1
 #else
+#define LWIP_NOASSERT               1
 #define LWIP_STATS                  0
 #endif