diff --git a/libraries/AP_NavEKF2/AP_NavEKF2.cpp b/libraries/AP_NavEKF2/AP_NavEKF2.cpp
index 5d432f9f5e..d06561315b 100644
--- a/libraries/AP_NavEKF2/AP_NavEKF2.cpp
+++ b/libraries/AP_NavEKF2/AP_NavEKF2.cpp
@@ -832,7 +832,7 @@ void NavEKF2::UpdateFilter(void)
 void NavEKF2::checkLaneSwitch(void)
 {
     AP::dal().log_event2(AP_DAL::Event2::checkLaneSwitch);
-    uint32_t now = AP::dal().millis();
+    const uint32_t now = AP::dal().millis();
     if (lastLaneSwitch_ms != 0 && now - lastLaneSwitch_ms < 5000) {
         // don't switch twice in 5 seconds
         return;