diff --git a/libraries/AP_Compass/CompassCalibrator.cpp b/libraries/AP_Compass/CompassCalibrator.cpp
index f33cb3998b..ffbcfd3aa1 100644
--- a/libraries/AP_Compass/CompassCalibrator.cpp
+++ b/libraries/AP_Compass/CompassCalibrator.cpp
@@ -797,6 +797,9 @@ bool CompassCalibrator::calculate_orientation(void)
         return true;
     }
 
+    // this function is very slow
+    hal.scheduler->expect_delay_ms(1000);
+
     float variance[ROTATION_MAX] {};
 
     for (enum Rotation r = ROTATION_NONE; r<ROTATION_MAX; r = (enum Rotation)(r+1)) {
@@ -863,6 +866,8 @@ bool CompassCalibrator::calculate_orientation(void)
         gcs().send_text(MAV_SEVERITY_INFO, "Mag(%u) new orientation: %u was %u %.1f", _compass_idx, besti, _orientation, _orientation_confidence);
     }
 
+    hal.scheduler->expect_delay_ms(0);
+    
     if (!pass) {
         set_status(COMPASS_CAL_BAD_ORIENTATION);
         return false;