diff --git a/libraries/AP_NavEKF2/AP_NavEKF2_core.h b/libraries/AP_NavEKF2/AP_NavEKF2_core.h
index 0188fb890e..78ab4b6f5f 100644
--- a/libraries/AP_NavEKF2/AP_NavEKF2_core.h
+++ b/libraries/AP_NavEKF2/AP_NavEKF2_core.h
@@ -20,7 +20,7 @@
  */
 #pragma once
 
-#pragma GCC optimize("O3")
+#pragma GCC optimize("O2")
 
 #define EK2_DISABLE_INTERRUPTS 0