diff --git a/libraries/net/eth/lwip-eth/arch/lpc17_emac.c b/libraries/net/eth/lwip-eth/arch/lpc17_emac.c
index 06772f48f1..102efb0a26 100644
--- a/libraries/net/eth/lwip-eth/arch/lpc17_emac.c
+++ b/libraries/net/eth/lwip-eth/arch/lpc17_emac.c
@@ -424,10 +424,31 @@ static struct pbuf *lpc_low_level_input(struct netif *netif)
 			p = lpc_enetif->rxb[idx];
 			p->len = (u16_t) length;
 
-			/* Free pbuf from desriptor */
+			/* Free pbuf from descriptor */
 			lpc_enetif->rxb[idx] = NULL;
 			lpc_enetif->rx_free_descs++;
 
+			/* Attempt to queue new buffer(s) */
+			if (lpc_rx_queue(lpc_enetif->netif) == 0) {
+    			/* Drop the frame due to OOM. */
+    			LINK_STATS_INC(link.drop);
+
+    			/* Re-queue the pbuf for receive */
+    			lpc_rxqueue_pbuf(lpc_enetif, p);
+
+    			LWIP_DEBUGF(UDP_LPC_EMAC | LWIP_DBG_TRACE,
+    				("lpc_low_level_input: Packet index %d dropped for OOM\n",
+    				idx));
+			
+#ifdef LOCK_RX_THREAD
+#if NO_SYS == 0
+        		sys_mutex_unlock(&lpc_enetif->TXLockMutex);
+#endif
+#endif
+
+		        return NULL;
+			}
+
 			LWIP_DEBUGF(UDP_LPC_EMAC | LWIP_DBG_TRACE,
 				("lpc_low_level_input: Packet received: %p, size %d (index=%d)\n",
 				p, length, idx));
@@ -435,9 +456,6 @@ static struct pbuf *lpc_low_level_input(struct netif *netif)
 			/* Save size */
 			p->tot_len = (u16_t) length;
 			LINK_STATS_INC(link.recv);
-
-			/* Queue new buffer(s) */
-			lpc_rx_queue(lpc_enetif->netif);
 		}
 	}
 
diff --git a/libraries/net/lwip/lwip-sys/arch/sys_arch.h b/libraries/net/lwip/lwip-sys/arch/sys_arch.h
index e6da8e9fbf..909532eb2f 100644
--- a/libraries/net/lwip/lwip-sys/arch/sys_arch.h
+++ b/libraries/net/lwip/lwip-sys/arch/sys_arch.h
@@ -51,7 +51,7 @@ typedef struct {
     osMessageQId    id;
     osMessageQDef_t def;
 #ifdef CMSIS_OS_RTX
-    uint32_t        queue[MB_SIZE];
+    uint32_t        queue[4+MB_SIZE]; /* The +4 is required for RTX OS_MCB overhead. */
 #endif
 } sys_mbox_t;
 
diff --git a/libraries/net/lwip/lwip/lwipopts.h b/libraries/net/lwip/lwip/lwipopts.h
index 42e36f1112..10846e2416 100644
--- a/libraries/net/lwip/lwip/lwipopts.h
+++ b/libraries/net/lwip/lwip/lwipopts.h
@@ -29,14 +29,14 @@
 
 #define LWIP_RAW                    0
 
-#define TCPIP_MBOX_SIZE             6
-#define DEFAULT_TCP_RECVMBOX_SIZE   6
-#define DEFAULT_UDP_RECVMBOX_SIZE   6
-#define DEFAULT_RAW_RECVMBOX_SIZE   6
-#define DEFAULT_ACCEPTMBOX_SIZE     6
+#define TCPIP_MBOX_SIZE             8
+#define DEFAULT_TCP_RECVMBOX_SIZE   8
+#define DEFAULT_UDP_RECVMBOX_SIZE   8
+#define DEFAULT_RAW_RECVMBOX_SIZE   8
+#define DEFAULT_ACCEPTMBOX_SIZE     8
 
 #define TCPIP_THREAD_STACKSIZE      1024
-#define TCPIP_THREAD_PRIO           1
+#define TCPIP_THREAD_PRIO           (osPriorityNormal)
 
 #define DEFAULT_THREAD_STACKSIZE    512