diff --git a/src/api/api_lib.c b/src/api/api_lib.c
index b92cf3b9..9c7b249f 100644
--- a/src/api/api_lib.c
+++ b/src/api/api_lib.c
@@ -642,8 +642,8 @@ netconn_recv_data_tcp(struct netconn *conn, struct pbuf **new_buf, u8_t apiflags
 #endif /* LWIP_TCP */
 
   if (!sys_mbox_valid(&conn->recvmbox)) {
-    /* This happens when calling this function after receiving FIN */
-    return sys_mbox_valid(&conn->acceptmbox) ? ERR_CONN : ERR_CLSD;
+    /* This only happens when calling this function more than once *after* receiving FIN */
+    return ERR_CONN;
   }
 
   if (!(apiflags & NETCONN_NOAUTORCVD)) {