diff --git a/libraries/AC_WPNav/AC_Circle.cpp b/libraries/AC_WPNav/AC_Circle.cpp
index 51b29d651b..14e74d2e7d 100644
--- a/libraries/AC_WPNav/AC_Circle.cpp
+++ b/libraries/AC_WPNav/AC_Circle.cpp
@@ -150,6 +150,13 @@ void AC_Circle::set_radius(float radius_cm)
     calc_velocities(false);
 }
 
+/// returns true if update has been run recently
+/// used by vehicle code to determine if get_yaw() is valid
+bool AC_Circle::is_active() const
+{
+    return (AP_HAL::millis() - _last_update_ms < 200);
+}
+
 /// update - update circle controller
 bool AC_Circle::update()
 {
@@ -219,6 +226,9 @@ bool AC_Circle::update()
     // update position controller
     _pos_control.update_xy_controller();
 
+    // set update time
+    _last_update_ms = AP_HAL::millis();
+
     return true;
 }
 
diff --git a/libraries/AC_WPNav/AC_Circle.h b/libraries/AC_WPNav/AC_Circle.h
index 177417e173..63143128b0 100644
--- a/libraries/AC_WPNav/AC_Circle.h
+++ b/libraries/AC_WPNav/AC_Circle.h
@@ -68,6 +68,10 @@ public:
     float get_pitch() const { return _pos_control.get_pitch(); }
     float get_yaw() const { return _yaw; }
 
+    /// returns true if update has been run recently
+    /// used by vehicle code to determine if get_yaw() is valid
+    bool is_active() const;
+
     // get_closest_point_on_circle - returns closest point on the circle
     //  circle's center should already have been set
     //  closest point on the circle will be placed in result
@@ -136,6 +140,7 @@ private:
     float       _angular_vel;   // angular velocity in radians/sec
     float       _angular_vel_max;   // maximum velocity in radians/sec
     float       _angular_accel; // angular acceleration in radians/sec/sec
+    uint32_t    _last_update_ms;    // system time of last update
 
     // terrain following variables
     bool        _terrain_alt;           // true if _center.z is alt-above-terrain, false if alt-above-ekf-origin