diff --git a/src/protocols/LoRaWAN/LoRaWAN.cpp b/src/protocols/LoRaWAN/LoRaWAN.cpp
index 866ce109..7a5bcf4b 100644
--- a/src/protocols/LoRaWAN/LoRaWAN.cpp
+++ b/src/protocols/LoRaWAN/LoRaWAN.cpp
@@ -1174,6 +1174,7 @@ int16_t LoRaWANNode::downlinkCommon() {
 
     // open Rx window by starting receive with specified timeout
     state = this->phyLayer->startReceive(timeoutMod, irqFlags, irqMask, 0);
+    RADIOLIB_ASSERT(state);
     RADIOLIB_DEBUG_PROTOCOL_PRINTLN("Opening Rx%d window (%d us timeout)... <-- Rx Delay end ", i+1, (int)timeoutHost);
     
     // wait for the timeout to complete (and a small additional delay)