diff --git a/libraries/AP_InertialSensor/AP_InertialSensor.cpp b/libraries/AP_InertialSensor/AP_InertialSensor.cpp
index ea6cc73b83..939c22b00e 100644
--- a/libraries/AP_InertialSensor/AP_InertialSensor.cpp
+++ b/libraries/AP_InertialSensor/AP_InertialSensor.cpp
@@ -742,17 +742,8 @@ AP_InertialSensor::init(uint16_t loop_rate)
     _calculated_harmonic_notch_freq_hz[0] = _harmonic_notch_filter.center_freq_hz();
     _num_calculated_harmonic_notch_frequencies = 1;
 
-    uint8_t harmonics = _harmonic_notch_filter.harmonics();
-    // allocate INS_MAX_NOTCHES as harmonics if using DynamicHarmonic
-    if (_harmonic_notch_filter.hasOption(HarmonicNotchFilterParams::Options::DynamicHarmonic)) {
-        harmonics = 0;
-        for (uint8_t h = 0; h < INS_MAX_NOTCHES; h++) {
-            harmonics = (harmonics << 1) + 1;
-        }
-    }
-
     for (uint8_t i=0; i<get_gyro_count(); i++) {
-        _gyro_harmonic_notch_filter[i].allocate_filters(harmonics, _harmonic_notch_filter.hasOption(HarmonicNotchFilterParams::Options::DoubleNotch));
+        _gyro_harmonic_notch_filter[i].allocate_filters(_harmonic_notch_filter.harmonics(), _harmonic_notch_filter.hasOption(HarmonicNotchFilterParams::Options::DoubleNotch));
         // initialise default settings, these will be subsequently changed in AP_InertialSensor_Backend::update_gyro()
         _gyro_harmonic_notch_filter[i].init(_gyro_raw_sample_rates[i], _calculated_harmonic_notch_freq_hz[0],
              _harmonic_notch_filter.bandwidth_hz(), _harmonic_notch_filter.attenuation_dB());