diff --git a/src/api/api_lib.c b/src/api/api_lib.c
index 02d284b1..fd2c9f2a 100644
--- a/src/api/api_lib.c
+++ b/src/api/api_lib.c
@@ -467,6 +467,7 @@ netconn_recv(struct netconn *conn)
   struct api_msg *msg;
   struct netbuf *buf;
   struct pbuf *p;
+  u16_t len;
     
   if(conn == NULL) {
     return NULL;
@@ -497,12 +498,17 @@ netconn_recv(struct netconn *conn)
     
     sys_mbox_fetch(conn->recvmbox, (void **)&p);
 
-    if (p != NULL) {
-      conn->recv_avail -= p->tot_len;
-      /* Register event with callback */
-      if (conn->callback)
-        (*conn->callback)(conn, NETCONN_EVT_RCVMINUS, p->tot_len);
+    if (p != NULL)
+    {
+        len = p->tot_len;
+        conn->recv_avail -= len;
     }
+    else
+        len = 0;
+    
+    /* Register event with callback */
+      if (conn->callback)
+        (*conn->callback)(conn, NETCONN_EVT_RCVMINUS, len);
 
     /* If we are closed, we indicate that we no longer wish to recieve
        data by setting conn->recvmbox to SYS_MBOX_NULL. */
diff --git a/src/api/api_msg.c b/src/api/api_msg.c
index c3b84375..c9924212 100644
--- a/src/api/api_msg.c
+++ b/src/api/api_msg.c
@@ -42,7 +42,8 @@ static err_t
 recv_tcp(void *arg, struct tcp_pcb *pcb, struct pbuf *p, err_t err)
 {
   struct netconn *conn;
-
+  u16_t len;
+  
   conn = arg;
 
   if(conn == NULL) {
@@ -54,11 +55,14 @@ recv_tcp(void *arg, struct tcp_pcb *pcb, struct pbuf *p, err_t err)
     	  
     conn->err = err;
     if (p != NULL) {
-      conn->recv_avail += p->tot_len;
-      /* Register event with callback */
-      if (conn->callback)
-        (*conn->callback)(conn, NETCONN_EVT_RCVPLUS, p->tot_len);
-    }  
+        len = p->tot_len;
+        conn->recv_avail += len;
+    }
+    else
+        len = 0;
+    /* Register event with callback */
+    if (conn->callback)
+        (*conn->callback)(conn, NETCONN_EVT_RCVPLUS, len);
     sys_mbox_post(conn->recvmbox, p);
   }  
   return ERR_OK;
diff --git a/src/include/lwip/sys.h b/src/include/lwip/sys.h
index 46669868..0aeac0fc 100644
--- a/src/include/lwip/sys.h
+++ b/src/include/lwip/sys.h
@@ -114,7 +114,7 @@ u32_t sys_arch_protect(void);
 void sys_arch_unprotect(u32_t pval);
 
 /* Thread functions. */
-void sys_thread_new(void (* thread)(void *arg), void *arg);
+sys_thread_t sys_thread_new(void (* thread)(void *arg), void *arg);
 
 /* The following functions are used only in Unix code, and
    can be omitted when porting the stack. */