diff --git a/ndn-cpp/c/transport/udp-transport.h b/ndn-cpp/c/transport/udp-transport.h
index c9f0d55..be60ab6 100644
--- a/ndn-cpp/c/transport/udp-transport.h
+++ b/ndn-cpp/c/transport/udp-transport.h
@@ -53,6 +53,7 @@
 
 /**
  * Check if there is data ready on the socket to be received with ndn_UdpTransport_receive.
+ * This does not block, and returns immediately.
  * @param self A pointer to the ndn_UdpTransport struct.
  * @param receiveIsReady This will be set to 1 if data is ready, 0 if not.
  * @return 0 for success, else an error code.