diff --git a/libraries/AP_AHRS/AP_AHRS.h b/libraries/AP_AHRS/AP_AHRS.h
index 9c6fee20f0..10acceca3a 100644
--- a/libraries/AP_AHRS/AP_AHRS.h
+++ b/libraries/AP_AHRS/AP_AHRS.h
@@ -199,7 +199,7 @@ protected:
     Vector3f        _accel_ef;
 
     // acceleration due to gravity in m/s/s
-    static const float _gravity = 9.80665;
+    static constexpr float _gravity = 9.80665;
 
 };