diff --git a/src/api/api_lib.c b/src/api/api_lib.c
index 25106d60..b334dca9 100644
--- a/src/api/api_lib.c
+++ b/src/api/api_lib.c
@@ -418,7 +418,7 @@ netconn_recv_tcp_pbuf(struct netconn *conn, struct pbuf **new_buf)
   LWIP_ERROR("netconn_recv: invalid conn", (conn != NULL) &&
              netconn_type(conn) == NETCONN_TCP, return ERR_ARG;);
 
-  return netconn_recv_data(conn, new_buf);
+  return netconn_recv_data(conn, (void **)new_buf);
 }
 
 /**
@@ -451,7 +451,7 @@ netconn_recv(struct netconn *conn, struct netbuf **new_buf)
       return ERR_MEM;
     }
 
-    err = netconn_recv_data(conn, &p);
+    err = netconn_recv_data(conn, (void **)&p);
     if (err != ERR_OK) {
       memp_free(MEMP_NETBUF, buf);
       return err;
@@ -468,7 +468,7 @@ netconn_recv(struct netconn *conn, struct netbuf **new_buf)
 #endif /* LWIP_TCP */
   } else {
 #if (LWIP_UDP || LWIP_RAW)
-    return netconn_recv_data(conn, new_buf);
+    return netconn_recv_data(conn, (void **)new_buf);
 #endif /* (LWIP_UDP || LWIP_RAW) */
   }
 }
diff --git a/src/api/sockets.c b/src/api/sockets.c
index 988437e8..a67c4772 100644
--- a/src/api/sockets.c
+++ b/src/api/sockets.c
@@ -578,9 +578,9 @@ lwip_recvfrom(int s, void *mem, size_t len, int flags,
       /* No data was left from the previous operation, so we try to get
          some from the network. */
       if (netconn_type(sock->conn) == NETCONN_TCP) {
-        err = netconn_recv_tcp_pbuf(sock->conn, &(struct pbuf *)buf);
+        err = netconn_recv_tcp_pbuf(sock->conn, (struct pbuf **)&buf);
       } else {
-        err = netconn_recv(sock->conn, &(struct netbuf *)buf);
+        err = netconn_recv(sock->conn, (struct netbuf **)&buf);
       }
       LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_recvfrom: netconn_recv err=%d, netbuf=%p\n",
         err, buf));
diff --git a/src/core/tcp_out.c b/src/core/tcp_out.c
index 6f244736..4118a253 100644
--- a/src/core/tcp_out.c
+++ b/src/core/tcp_out.c
@@ -124,7 +124,7 @@ tcp_create_segment(struct tcp_pcb *pcb, struct pbuf *p, u8_t flags, u32_t seqno,
   struct tcp_seg *seg;
   u8_t optlen = LWIP_TCP_OPT_LENGTH(optflags);
 
-  if ((seg = memp_malloc(MEMP_TCP_SEG)) == NULL) {
+  if ((seg = (struct tcp_seg *)memp_malloc(MEMP_TCP_SEG)) == NULL) {
     LWIP_DEBUGF(TCP_OUTPUT_DEBUG | 2, ("tcp_create_segment: no memory.\n"));
     pbuf_free(p);
     return NULL;
@@ -142,7 +142,7 @@ tcp_create_segment(struct tcp_pcb *pcb, struct pbuf *p, u8_t flags, u32_t seqno,
     tcp_seg_free(seg);
     return NULL;
   }
-  seg->tcphdr = seg->p->payload;
+  seg->tcphdr = (struct tcp_hdr *)seg->p->payload;
   seg->tcphdr->src = htons(pcb->local_port);
   seg->tcphdr->dest = htons(pcb->remote_port);
   seg->tcphdr->seqno = htonl(seqno);