diff --git a/arduino/hev_prototype_v1/src/BreathingLoop.cpp b/arduino/hev_prototype_v1/src/BreathingLoop.cpp
index 59de416fd4c7a2c873666f2a94125997fe7b99c0..e6a215a956d4080b2eb5ab1b012d382d2ffbce98 100644
--- a/arduino/hev_prototype_v1/src/BreathingLoop.cpp
+++ b/arduino/hev_prototype_v1/src/BreathingLoop.cpp
@@ -54,7 +54,7 @@ void BreathingLoop::updateReadings()
         _readings_time = tnow;
         _readings_N++;
 
-        _readings_sums.timestamp                += tnow;
+        _readings_sums.timestamp                = tnow;
 #ifdef CHIP_ESP32
         _readings_sums.pressure_air_supply      += static_cast<uint32_t>(analogRead(pin_pressure_air_supply)    );
         _readings_sums.pressure_o2_supply       += static_cast<uint32_t>(analogRead(pin_pressure_o2_supply)     );