diff --git a/src/gui/menu_general.cpp b/src/gui/menu_general.cpp
index 7072b11aa..b5b37e0d3 100644
--- a/src/gui/menu_general.cpp
+++ b/src/gui/menu_general.cpp
@@ -991,7 +991,7 @@ void menuGeneralDiagAna(uint8_t event)
   lcd_putsLeft(6*FH+1, STR_BATT_CALIB);
   static uint32_t adcBatt;
   adcBatt = ((adcBatt * 7) + anaIn(8)) / 8; // running average, sourced directly (to avoid unending debate :P)
-  uint32_t batCalV = ( adcBatt + adcBatt*(g_eeGeneral.vBatCalib)/128 ) * BATT_SCALE;
+  uint32_t batCalV = ( adcBatt + ((int32_t)adcBatt*g_eeGeneral.vBatCalib)/128 ) * BATT_SCALE;
   batCalV >>= 11;
   batCalV += 2; // because of the diode
   putsVolts(LEN_CALIB_FIELDS*FW+4*FW, 6*FH+1, batCalV, (m_posVert==1 ? INVERS : 0));