diff --git a/libraries/ESP8266WiFi/src/include/UdpContext.h b/libraries/ESP8266WiFi/src/include/UdpContext.h
index 540217d2fa..59403dbdf8 100644
--- a/libraries/ESP8266WiFi/src/include/UdpContext.h
+++ b/libraries/ESP8266WiFi/src/include/UdpContext.h
@@ -475,7 +475,7 @@ class UdpContext
             }
             // construct in place
             new(PBUF_ALIGNER(pb_helper->payload)) AddrHelper(srcaddr, TEMPDSTADDR, srcport);
-            pb->flags = PBUF_HELPER_FLAG; // mark helper pbuf
+            pb_helper->flags = PBUF_HELPER_FLAG; // mark helper pbuf
             // chain it
             pbuf_cat(_rx_buf, pb_helper);