diff --git a/libraries/AP_InertialSensor/AP_InertialSensor.cpp b/libraries/AP_InertialSensor/AP_InertialSensor.cpp
index 5fd4c5f6e8..a75430b8ff 100644
--- a/libraries/AP_InertialSensor/AP_InertialSensor.cpp
+++ b/libraries/AP_InertialSensor/AP_InertialSensor.cpp
@@ -1848,6 +1848,7 @@ MAV_RESULT AP_InertialSensor::simple_accel_cal()
         return MAV_RESULT_TEMPORARILY_REJECTED;
     }
 
+    hal.scheduler->expect_delay_ms(20000);
     // record we are calibrating
     _calibrating = true;
 
@@ -1987,6 +1988,8 @@ MAV_RESULT AP_InertialSensor::simple_accel_cal()
     // stop flashing leds
     AP_Notify::flags.initialising = false;
 
+    hal.scheduler->expect_delay_ms(0);
+
     return result;
 }