diff --git a/libraries/AP_InertialSensor/AP_InertialSensor_Backend.cpp b/libraries/AP_InertialSensor/AP_InertialSensor_Backend.cpp
index 2aeffb24cb..8d22990afe 100644
--- a/libraries/AP_InertialSensor/AP_InertialSensor_Backend.cpp
+++ b/libraries/AP_InertialSensor/AP_InertialSensor_Backend.cpp
@@ -817,8 +817,7 @@ void AP_InertialSensor_Backend::update_primary()
     uint32_t now_us = AP_HAL::micros();
     if (is_primary != is_new_primary
         || AP_HAL::timeout_expired(last_primary_update_us, now_us, PRIMARY_UPDATE_TIMEOUT_US)) {
-        set_primary_gyro(is_new_primary);
-        set_primary_accel(is_new_primary);
+        set_primary(is_new_primary);
         is_primary = is_new_primary;
         last_primary_update_us = now_us;
     }
diff --git a/libraries/AP_InertialSensor/AP_InertialSensor_Backend.h b/libraries/AP_InertialSensor/AP_InertialSensor_Backend.h
index 29b49910a1..f98925dd10 100644
--- a/libraries/AP_InertialSensor/AP_InertialSensor_Backend.h
+++ b/libraries/AP_InertialSensor/AP_InertialSensor_Backend.h
@@ -296,8 +296,7 @@ protected:
 
     // catch updates to the primary gyro and accel
     void update_primary() __RAMFUNC__; /* backend */
-    virtual void set_primary_gyro(bool is_primary_gyro) {}
-    virtual void set_primary_accel(bool is_primary_accel) {}
+    virtual void set_primary(bool _is_primary) {}
 
     // support for updating filter at runtime
     uint16_t _last_accel_filter_hz;
diff --git a/libraries/AP_InertialSensor/AP_InertialSensor_Invensensev3.cpp b/libraries/AP_InertialSensor/AP_InertialSensor_Invensensev3.cpp
index 2c0ca4994b..33b8cd3f6f 100644
--- a/libraries/AP_InertialSensor/AP_InertialSensor_Invensensev3.cpp
+++ b/libraries/AP_InertialSensor/AP_InertialSensor_Invensensev3.cpp
@@ -401,14 +401,15 @@ bool AP_InertialSensor_Invensensev3::update()
     return true;
 }
 
-void AP_InertialSensor_Invensensev3::set_primary_gyro(bool _is_primary)
+void AP_InertialSensor_Invensensev3::set_primary(bool _is_primary)
 {
 #if AP_INERTIALSENSOR_FAST_SAMPLE_WINDOW_ENABLED
     if (_imu.is_dynamic_fifo_enabled(gyro_instance)) {
         if (_is_primary) {
             dev->adjust_periodic_callback(periodic_handle, backend_period_us);
         } else {
-            dev->adjust_periodic_callback(periodic_handle, backend_period_us * get_fast_sampling_rate());
+            // scale down non-primary to loop rate
+            dev->adjust_periodic_callback(periodic_handle, 1000000UL / get_loop_rate_hz());
         }
     }
 #endif
diff --git a/libraries/AP_InertialSensor/AP_InertialSensor_Invensensev3.h b/libraries/AP_InertialSensor/AP_InertialSensor_Invensensev3.h
index 2c20db6914..2ea558b3fd 100644
--- a/libraries/AP_InertialSensor/AP_InertialSensor_Invensensev3.h
+++ b/libraries/AP_InertialSensor/AP_InertialSensor_Invensensev3.h
@@ -46,7 +46,7 @@ public:
     const uint16_t multiplier_accel = INT16_MAX/(32*GRAVITY_MSS);
 
 protected:
-    void set_primary_gyro(bool is_primary) override;
+    void set_primary(bool _is_primary) override;
 
 private:
     AP_InertialSensor_Invensensev3(AP_InertialSensor &imu,