diff --git a/bbn_wave_freq_m5atomS3/bbn_wave_freq_m5atomS3.ino b/bbn_wave_freq_m5atomS3/bbn_wave_freq_m5atomS3.ino
index a4de925..145cb39 100644
--- a/bbn_wave_freq_m5atomS3/bbn_wave_freq_m5atomS3.ino
+++ b/bbn_wave_freq_m5atomS3/bbn_wave_freq_m5atomS3.ino
@@ -24,6 +24,7 @@
 #include "TrochoidalWave.h"
 #include "Mahony_AHRS.h"
 #include "Quaternion.h"
+#include "MonoWedge.h"
 
 // Strength of the calibration operation;
 // 0: disables calibration.