diff --git a/src/TypeDef.h b/src/TypeDef.h
index da3eccc8..1d59bf6c 100644
--- a/src/TypeDef.h
+++ b/src/TypeDef.h
@@ -499,7 +499,7 @@
 #define RADIOLIB_ERR_INVALID_REVISION                           (-1103)
 
 /*!
-  \brief Invalid LoRaWAN uplink port requested by user.
+  \brief Invalid LoRaWAN uplink port requested by user, or downlink received at invalid port.
 */
 #define RADIOLIB_ERR_INVALID_PORT                               (-1104)
 
diff --git a/src/protocols/LoRaWAN/LoRaWAN.cpp b/src/protocols/LoRaWAN/LoRaWAN.cpp
index e61c0045..3958c497 100644
--- a/src/protocols/LoRaWAN/LoRaWAN.cpp
+++ b/src/protocols/LoRaWAN/LoRaWAN.cpp
@@ -877,9 +877,13 @@ int16_t LoRaWANNode::uplink(uint8_t* data, size_t len, uint8_t fPort, bool isCon
   }
 
   // check destination fPort
-  if(fPort > 0xDF) {
+  if(fPort > RADIOLIB_LORAWAN_FPORT_RESERVED) {
+    RADIOLIB_DEBUG_PROTOCOL_PRINTLN("Requested uplink at FPort %d - rejected! This FPort is RFU.", fPort);
     return(RADIOLIB_ERR_INVALID_PORT);
   }
+  if(fPort == RADIOLIB_LORAWAN_FPORT_TS009 && this->TS009 == false) {
+    RADIOLIB_DEBUG_PROTOCOL_PRINTLN("Requested uplink at FPort %d - rejected! TS009 was not enabled.", fPort);
+  }
   // fPort 0 is only allowed for MAC-only payloads
   if(fPort == RADIOLIB_LORAWAN_FPORT_MAC_COMMAND) {
     if (!this->isMACPayload) {
@@ -900,9 +904,12 @@ int16_t LoRaWANNode::uplink(uint8_t* data, size_t len, uint8_t fPort, bool isCon
 
   // check maximum payload len as defined in phy
   if(len > this->band->payloadLenMax[this->dataRates[RADIOLIB_LORAWAN_CHANNEL_DIR_UPLINK]]) {
-    return(RADIOLIB_ERR_PACKET_TOO_LONG);
-    // if testing with TS009 specification verification protocol, don't throw error but clip the message
-    // len = this->band->payloadLenMax[this->dataRates[RADIOLIB_LORAWAN_CHANNEL_DIR_UPLINK]];
+    // normally, throw an error if the packet is too long
+    if(this->TS009 == false) {
+      return(RADIOLIB_ERR_PACKET_TOO_LONG);
+    }
+    // if testing with TS009 Specification Verification Protocol, don't throw error but clip the message
+    len = this->band->payloadLenMax[this->dataRates[RADIOLIB_LORAWAN_CHANNEL_DIR_UPLINK]];
   }
 
   bool adrAckReq = false;
@@ -1383,6 +1390,22 @@ int16_t LoRaWANNode::downlink(uint8_t* data, size_t* len, LoRaWANEvent_t* event)
   if(payLen > 0) {
     payLen -= 1;  // subtract one as fPort is set
     fPort = downlinkMsg[RADIOLIB_LORAWAN_FHDR_FPORT_POS(fOptsLen)];
+    // check if fPort value is actually allowed
+    if(fPort > RADIOLIB_LORAWAN_FPORT_RESERVED) {
+      RADIOLIB_DEBUG_PROTOCOL_PRINTLN("Received downlink at FPort %d - rejected! This FPort is RFU!", fPort);
+      #if !RADIOLIB_STATIC_ONLY
+        delete[] downlinkMsg;
+      #endif
+      return(RADIOLIB_ERR_INVALID_PORT);
+    }
+    if(fPort == RADIOLIB_LORAWAN_FPORT_TS009 && this->TS009 == false) {
+      RADIOLIB_DEBUG_PROTOCOL_PRINTLN("Received downlink at FPort %d - rejected! TS009 was not enabled.", fPort);
+      #if !RADIOLIB_STATIC_ONLY
+        delete[] downlinkMsg;
+      #endif
+      return(RADIOLIB_ERR_INVALID_PORT);
+    }
+
     if(fPort > RADIOLIB_LORAWAN_FPORT_MAC_COMMAND) {
       isAppDownlink = true;
     } else {
diff --git a/src/protocols/LoRaWAN/LoRaWAN.h b/src/protocols/LoRaWAN/LoRaWAN.h
index 674b0189..f9c8ab8f 100644
--- a/src/protocols/LoRaWAN/LoRaWAN.h
+++ b/src/protocols/LoRaWAN/LoRaWAN.h
@@ -41,7 +41,8 @@
 
 // fPort field
 #define RADIOLIB_LORAWAN_FPORT_MAC_COMMAND                      (0x00 << 0) //  7     0     payload contains MAC commands only
-#define RADIOLIB_LORAWAN_FPORT_RESERVED                         (0xE0 << 0) //  7     0     reserved fPort values
+#define RADIOLIB_LORAWAN_FPORT_TS009                            (0xE0 << 0) //  7     0     fPort used for TS009 testing
+#define RADIOLIB_LORAWAN_FPORT_RESERVED                         (0xE0 << 0) //  7     0     fPort values equal to and larger than this are reserved
 
 // MAC commands - only those sent from end-device to gateway
 #define RADIOLIB_LORAWAN_LINK_CHECK_REQ                         (0x02 << 0) //  7     0     MAC command: request to check connectivity to network
@@ -849,10 +850,16 @@ class LoRaWANNode {
     uint64_t getDevAddr();
 
     /*!
-      \brief Get the Time-on-air of the last uplink message
-      \returns (RadioLibTime_t) time-on-air (ToA) of last uplink message
+      \brief Get the Time-on-air of the last uplink message.
+      \returns (RadioLibTime_t) time-on-air (ToA) of last uplink message.
     */
-   RadioLibTime_t getLastToA();
+    RadioLibTime_t getLastToA();
+
+    /*! 
+      \brief TS009 Protocol Specification Verification switch
+      (allows FPort 224 and cuts off uplink payload instead of rejecting if maximum length exceeded).
+    */
+    bool TS009 = false;
 
 #if !RADIOLIB_GODMODE
   private: