diff --git a/libraries/AP_GPS/AP_GPS_GSOF.cpp b/libraries/AP_GPS/AP_GPS_GSOF.cpp
index af79dd2339bca7..2df59bb828922e 100644
--- a/libraries/AP_GPS/AP_GPS_GSOF.cpp
+++ b/libraries/AP_GPS/AP_GPS_GSOF.cpp
@@ -74,8 +74,13 @@ AP_GPS_GSOF::read(void)
     const uint32_t now = AP_HAL::millis();
 
     if (gsofmsgreq_index < (sizeof(gsofmsgreq))) {
+        const auto com_port = gps._com_port[state.instance].get();
+        if (!validate_com_port(com_port)) {
+            // The user parameter for COM port is not a valid GSOF port
+            return false;
+        }
         if (now > gsofmsg_time) {
-            requestGSOF(gsofmsgreq[gsofmsgreq_index], HW_Port::COM2, Output_Rate::FREQ_10_HZ);
+            requestGSOF(gsofmsgreq[gsofmsgreq_index], static_cast<HW_Port>(com_port), Output_Rate::FREQ_10_HZ);
             gsofmsg_time = now + 110;
             gsofmsgreq_index++;
         }
@@ -347,4 +352,16 @@ AP_GPS_GSOF::process_message(void)
 
     return false;
 }
+
+bool
+AP_GPS_GSOF::validate_com_port(const uint8_t com_port) const {
+    switch(com_port) {
+        case static_cast<uint8_t>(HW_Port::COM1):
+        case static_cast<uint8_t>(HW_Port::COM2):
+            return true;
+        default:
+            return false;
+    }
+}
+
 #endif
diff --git a/libraries/AP_GPS/AP_GPS_GSOF.h b/libraries/AP_GPS/AP_GPS_GSOF.h
index fe3b0cf8f6e64e..998a644de189cc 100644
--- a/libraries/AP_GPS/AP_GPS_GSOF.h
+++ b/libraries/AP_GPS/AP_GPS_GSOF.h
@@ -72,6 +72,7 @@ class AP_GPS_GSOF : public AP_GPS_Backend
     uint16_t SwapUint16(const uint8_t* src, const uint32_t pos) const WARN_IF_UNUSED;
 
     bool validate_baud(const uint8_t baud) const WARN_IF_UNUSED;
+    bool validate_com_port(const uint8_t com_port) const WARN_IF_UNUSED;
 
     struct Msg_Parser
     {