diff --git a/libraries/AP_NavEKF/AP_NavEKF.cpp b/libraries/AP_NavEKF/AP_NavEKF.cpp
index 1d1694df6f..7b05414781 100644
--- a/libraries/AP_NavEKF/AP_NavEKF.cpp
+++ b/libraries/AP_NavEKF/AP_NavEKF.cpp
@@ -2910,7 +2910,7 @@ void NavEKF::FuseOptFlow()
     Vector3f velNED_local;
     Vector3f relVelSensor;
 
-    uint8_t &obsIndex = flow_state.obsIndex;
+    uint8_t obsIndex = flow_state.obsIndex;
     ftype &q0 = flow_state.q0;
     ftype &q1 = flow_state.q1;
     ftype &q2 = flow_state.q2;