diff --git a/stm-firmware/include/reflow-controller/safety-adc.h b/stm-firmware/include/reflow-controller/safety-adc.h
index 75400ce..9a893fa 100644
--- a/stm-firmware/include/reflow-controller/safety-adc.h
+++ b/stm-firmware/include/reflow-controller/safety-adc.h
@@ -37,6 +37,7 @@ enum safety_adc_check_result {
 				SAFETY_ADC_CHECK_VREF_HIGH = (1U<<1),
 				SAFETY_ADC_CHECK_TEMP_LOW = (1U<<2),
 				SAFETY_ADC_CHECK_TEMP_HIGH = (1U<<3),
+				SAFETY_ADC_INTERNAL_ERROR = (1U<<4),
 				};
 
 void safety_adc_init();
diff --git a/stm-firmware/safety-adc.c b/stm-firmware/safety-adc.c
index 945fc93..7d5a6d3 100644
--- a/stm-firmware/safety-adc.c
+++ b/stm-firmware/safety-adc.c
@@ -132,7 +132,7 @@ enum safety_adc_check_result handle_safety_adc()
 			break;
 		default:
 			safety_meas_channel = SAFETY_ADC_MEAS_VREF;
-			return -2000;
+			return SAFETY_ADC_INTERNAL_ERROR;
 		}
 	}