diff --git a/libraries/AP_InertialSensor/AP_InertialSensor_rate_config.h b/libraries/AP_InertialSensor/AP_InertialSensor_rate_config.h
index b7305e76964a09..8bf45fecab7f05 100644
--- a/libraries/AP_InertialSensor/AP_InertialSensor_rate_config.h
+++ b/libraries/AP_InertialSensor/AP_InertialSensor_rate_config.h
@@ -7,7 +7,3 @@
 #ifndef AP_INERTIALSENSOR_FAST_SAMPLE_WINDOW_ENABLED
 #define AP_INERTIALSENSOR_FAST_SAMPLE_WINDOW_ENABLED (AP_INERTIALSENSOR_ENABLED && HAL_INS_RATE_LOOP && AP_INERTIALSENSOR_HARMONICNOTCH_ENABLED && APM_BUILD_TYPE(APM_BUILD_ArduCopter))
 #endif
-
-#ifndef AP_INERTIALSENSOR_DYNAMIC_FIFO_MASK
-#define AP_INERTIALSENSOR_DYNAMIC_FIFO_MASK 127
-#endif
diff --git a/libraries/AP_InertialSensor/FastRateBuffer.cpp b/libraries/AP_InertialSensor/FastRateBuffer.cpp
index b47450493d41ea..44ef58513982ef 100644
--- a/libraries/AP_InertialSensor/FastRateBuffer.cpp
+++ b/libraries/AP_InertialSensor/FastRateBuffer.cpp
@@ -85,8 +85,7 @@ bool AP_InertialSensor::is_dynamic_fifo_enabled(uint8_t instance) const
     if (!fast_rate_buffer_enabled || fast_rate_buffer == nullptr) {
         return false;
     }
-    return ((1U<<instance) & AP_INERTIALSENSOR_DYNAMIC_FIFO_MASK)
-            && (_fast_sampling_mask & (1U<<instance)) != 0
+    return (_fast_sampling_mask & (1U<<instance)) != 0
             && fast_rate_buffer->use_rate_loop_gyro_samples();
 }