diff --git a/src/modules/mavlink/streams/BATTERY_STATUS.hpp b/src/modules/mavlink/streams/BATTERY_STATUS.hpp
index 389631db87f7..73068f0de360 100644
--- a/src/modules/mavlink/streams/BATTERY_STATUS.hpp
+++ b/src/modules/mavlink/streams/BATTERY_STATUS.hpp
@@ -190,7 +190,7 @@ class MavlinkStreamBatteryStatus : public MavlinkStream
 							if (i < mavlink_cell_slots) {
 								bat_msg.voltages[i] = battery_status.voltage_cell_v[i] * 1000.f;
 
-							} else if (i < mavlink_cell_slots + mavlink_cell_slots_extension) {
+							} else if ((i - mavlink_cell_slots) < mavlink_cell_slots_extension) {
 								bat_msg.voltages_ext[i - mavlink_cell_slots] = battery_status.voltage_cell_v[i] * 1000.f;
 							}
 						}