diff --git a/ArduCopter/Copter.h b/ArduCopter/Copter.h
index 926b55d7f1..5a384ead58 100644
--- a/ArduCopter/Copter.h
+++ b/ArduCopter/Copter.h
@@ -608,6 +608,9 @@ private:
         float takeoff_alt_cm;
     } gndeffect_state;
 
+    // set when we are upgrading parameters from 3.4
+    bool upgrading_frame_params;
+    
     static const AP_Scheduler::Task scheduler_tasks[];
     static const AP_Param::Info var_info[];
     static const struct LogStructure log_structure[];
diff --git a/ArduCopter/Parameters.cpp b/ArduCopter/Parameters.cpp
index 1f3b9f1d8d..1f2d97a5d7 100644
--- a/ArduCopter/Parameters.cpp
+++ b/ArduCopter/Parameters.cpp
@@ -1164,25 +1164,7 @@ void Copter::convert_pid_parameters(void)
     const uint16_t old_aux_chan_mask = 0x3FF0;
     // note that we don't pass in rcmap as we don't want output channel functions changed based on rcmap
     if (SRV_Channels::upgrade_parameters(old_rc_keys, old_aux_chan_mask, nullptr)) {
-        // do frame specific upgrade. This is only done the first time we run the new firmware
-#if FRAME_CONFIG == HELI_FRAME
-        SRV_Channels::upgrade_motors_servo(Parameters::k_param_motors, 12, CH_1);
-        SRV_Channels::upgrade_motors_servo(Parameters::k_param_motors, 13, CH_2);
-        SRV_Channels::upgrade_motors_servo(Parameters::k_param_motors, 14, CH_3);
-        SRV_Channels::upgrade_motors_servo(Parameters::k_param_motors, 15, CH_4);
-#else
-        if (g2.frame_class == AP_Motors::MOTOR_FRAME_TRI) {
-            const AP_Param::ConversionInfo tri_conversion_info[] = {
-                { Parameters::k_param_motors, 32, AP_PARAM_INT16, "SERVO7_TRIM" },
-                { Parameters::k_param_motors, 33, AP_PARAM_INT16, "SERVO7_MIN" },
-                { Parameters::k_param_motors, 34, AP_PARAM_INT16, "SERVO7_MAX" },
-                { Parameters::k_param_motors, 35, AP_PARAM_FLOAT, "MOT_YAW_SV_ANGLE" },
-            };
-            // we need to use CONVERT_FLAG_FORCE as the SERVO7_* parameters will already be set from RC7_*
-            AP_Param::convert_old_parameters(tri_conversion_info, ARRAY_SIZE(tri_conversion_info), AP_Param::CONVERT_FLAG_FORCE);
-            const AP_Param::ConversionInfo tri_conversion_info_rev { Parameters::k_param_motors, 31, AP_PARAM_INT8,  "SERVO7_REVERSED" };
-            AP_Param::convert_old_parameter(&tri_conversion_info_rev, 1, AP_Param::CONVERT_FLAG_REVERSE | AP_Param::CONVERT_FLAG_FORCE);
-        }
-#endif
+        // the rest needs to be done after motors allocation
+        upgrading_frame_params = true;
     }
 }
diff --git a/ArduCopter/system.cpp b/ArduCopter/system.cpp
index 155d339018..9ecff11177 100644
--- a/ArduCopter/system.cpp
+++ b/ArduCopter/system.cpp
@@ -615,4 +615,29 @@ void Copter::allocate_motors(void)
     default:
         break;
     }
+
+    if (upgrading_frame_params) {
+        // do frame specific upgrade. This is only done the first time we run the new firmware
+#if FRAME_CONFIG == HELI_FRAME
+        SRV_Channels::upgrade_motors_servo(Parameters::k_param_motors, 12, CH_1);
+        SRV_Channels::upgrade_motors_servo(Parameters::k_param_motors, 13, CH_2);
+        SRV_Channels::upgrade_motors_servo(Parameters::k_param_motors, 14, CH_3);
+        SRV_Channels::upgrade_motors_servo(Parameters::k_param_motors, 15, CH_4);
+#else
+        if (g2.frame_class == AP_Motors::MOTOR_FRAME_TRI) {
+            const AP_Param::ConversionInfo tri_conversion_info[] = {
+                { Parameters::k_param_motors, 32, AP_PARAM_INT16, "SERVO7_TRIM" },
+                { Parameters::k_param_motors, 33, AP_PARAM_INT16, "SERVO7_MIN" },
+                { Parameters::k_param_motors, 34, AP_PARAM_INT16, "SERVO7_MAX" },
+                { Parameters::k_param_motors, 35, AP_PARAM_FLOAT, "MOT_YAW_SV_ANGLE" },
+            };
+            // we need to use CONVERT_FLAG_FORCE as the SERVO7_* parameters will already be set from RC7_*
+            AP_Param::convert_old_parameters(tri_conversion_info, ARRAY_SIZE(tri_conversion_info), AP_Param::CONVERT_FLAG_FORCE);
+            const AP_Param::ConversionInfo tri_conversion_info_rev { Parameters::k_param_motors, 31, AP_PARAM_INT8,  "SERVO7_REVERSED" };
+            AP_Param::convert_old_parameter(&tri_conversion_info_rev, 1, AP_Param::CONVERT_FLAG_REVERSE | AP_Param::CONVERT_FLAG_FORCE);
+            // AP_MotorsTri was converted from having nested var_info to one level
+            AP_Param::convert_parent_class(Parameters::k_param_motors, motors, motors->var_info);
+        }
+#endif
+    }
 }