diff --git a/Tools/autotest/common.py b/Tools/autotest/common.py
index 9d01c51a42..27053a329c 100644
--- a/Tools/autotest/common.py
+++ b/Tools/autotest/common.py
@@ -9173,7 +9173,7 @@ switch value'''
         while len(wants):
             self.progress("Still wanting (%s)" % ",".join([("0x%02x" % x) for x in wants.keys()]))
             wants_copy = copy.copy(wants)
-            t2 = self.get_sim_time_cached()
+            t2 = self.get_sim_time()
             if t2 - tstart > 300:
                 self.progress("Failed to get frsky passthrough data")
                 self.progress("Counts of sensor_id polls sent:")
@@ -9193,7 +9193,7 @@ switch value'''
 
     def test_frsky_passthrough(self):
         self.set_parameter("SERIAL5_PROTOCOL", 10) # serial5 is FRSky passthrough
-        self.set_parameter("RPM_TYPE", 1) # enable RPM output
+        self.set_parameter("RPM_TYPE", 10) # enable RPM output
         self.customise_SITL_commandline([
             "--uartF=tcp:6735" # serial5 spews to localhost:6735
         ])
diff --git a/libraries/AP_Frsky_Telem/AP_Frsky_Backend.h b/libraries/AP_Frsky_Telem/AP_Frsky_Backend.h
index b247fd5c88..15f80ace70 100644
--- a/libraries/AP_Frsky_Telem/AP_Frsky_Backend.h
+++ b/libraries/AP_Frsky_Telem/AP_Frsky_Backend.h
@@ -109,7 +109,8 @@ protected:
     static const uint8_t BYTESTUFF_D               = 0x5D;
 
     // FrSky data IDs;
-    static const uint16_t RPM_LAST_ID               = 0x050F;
+    static const uint16_t RPM1_ID                   = 0x050E;
+    static const uint16_t RPM2_ID                   = 0x050F;
     static const uint16_t GPS_LONG_LATI_FIRST_ID    = 0x0800;
     static const uint16_t DIY_FIRST_ID              = 0x5000;
 
diff --git a/libraries/AP_Frsky_Telem/AP_Frsky_SPort.cpp b/libraries/AP_Frsky_Telem/AP_Frsky_SPort.cpp
index 0449d6deab..3a1c7a3daa 100644
--- a/libraries/AP_Frsky_Telem/AP_Frsky_SPort.cpp
+++ b/libraries/AP_Frsky_Telem/AP_Frsky_SPort.cpp
@@ -126,9 +126,14 @@ void AP_Frsky_SPort::send(void)
                     int32_t value;
                     if (calc_rpm(_SPort.rpm_call, value)) {
                         // use high numbered frsky sensor ids to leave low numbered free for externally attached physical frsky sensors
-                        send_sport_frame(SPORT_DATA_FRAME, 1+RPM_LAST_ID-(rpm->num_sensors()-_SPort.rpm_call), value);
+                        uint16_t id = RPM1_ID;
+                        if (_SPort.rpm_call != 0) {
+                            // only two sensors are currently supported
+                            id = RPM2_ID;
+                        }
+                        send_sport_frame(SPORT_DATA_FRAME, id, value);
                     }
-                    if (++_SPort.rpm_call > (rpm->num_sensors()-1)) {
+                    if (++_SPort.rpm_call > MIN(rpm->num_sensors()-1, 1)) {
                         _SPort.rpm_call = 0;
                     }
                 }