diff --git a/Marlin/pins.h b/Marlin/pins.h
index e950cbe683..52aae6b7ed 100644
--- a/Marlin/pins.h
+++ b/Marlin/pins.h
@@ -111,6 +111,9 @@
 #endif
 #define PS_ON_PIN 15
 
+// Gen 1.3 and earlier supplied thermistor power via PS_ON
+// Need to ignore the bad thermistor readings on those units
+#define BOGUS_TEMPERATURE_FAILSAFE_OVERRIDE
 //our pin for debugging.
 #define DEBUG_PIN 0
 
diff --git a/Marlin/temperature.cpp b/Marlin/temperature.cpp
index 6efbbd1d94..069674be90 100644
--- a/Marlin/temperature.cpp
+++ b/Marlin/temperature.cpp
@@ -851,7 +851,7 @@ ISR(TIMER0_COMPB_vect)
     for(unsigned char e = 0; e < EXTRUDERS; e++) {
        if(current_raw[e] >= maxttemp[e]) {
           target_raw[e] = 0;
-          #if (PS_ON != -1)
+          #ifndef BOGUS_TEMPERATURE_FAILSAFE_OVERRIDE
           {
             max_temp_error(e);
             kill();;
@@ -860,7 +860,7 @@ ISR(TIMER0_COMPB_vect)
        }
        if(current_raw[e] <= minttemp[e]) {
           target_raw[e] = 0;
-          #if (PS_ON != -1)
+          #ifndef BOGUS_TEMPERATURE_FAILSAFE_OVERRIDE
           {
             min_temp_error(e);
             kill();