diff --git a/Marlin/Configuration.h b/Marlin/Configuration.h
index 685d2f8f93..374a420539 100644
--- a/Marlin/Configuration.h
+++ b/Marlin/Configuration.h
@@ -436,15 +436,9 @@
 #define DUMMY_THERMISTOR_998_VALUE 25
 #define DUMMY_THERMISTOR_999_VALUE 100
 
-// Resistor values when using a MAX31865 (sensor -5) on TEMP_SENSOR_0
-// Sensor value is typically 100 (PT100) or 1000 (PT1000)
-// Calibration value is typically 430 ohm for AdaFruit PT100 modules and 4300 ohm for AdaFruit PT1000 modules.
-//#define MAX31865_SENSOR_OHMS_0      100
-//#define MAX31865_CALIBRATION_OHMS_0 430
-
-// Resistor values when using a MAX31865 (sensor -5) on TEMP_SENSOR_1
-// Sensor value is typically 100 (PT100) or 1000 (PT1000)
-// Calibration value is typically 430 ohm for AdaFruit PT100 modules and 4300 ohm for AdaFruit PT1000 modules.
+// Resistor values when using MAX31865 sensors (-5) on TEMP_SENSOR_0 / 1
+//#define MAX31865_SENSOR_OHMS_0      100   // (Ω) Typically 100 or 1000 (PT100 or PT1000)
+//#define MAX31865_CALIBRATION_OHMS_0 430   // (Ω) Typically 430 for AdaFruit PT100; 4300 for AdaFruit PT1000
 //#define MAX31865_SENSOR_OHMS_1      100
 //#define MAX31865_CALIBRATION_OHMS_1 430
 
diff --git a/Marlin/src/module/temperature.cpp b/Marlin/src/module/temperature.cpp
index 9f042ff25c..98c1366a7e 100644
--- a/Marlin/src/module/temperature.cpp
+++ b/Marlin/src/module/temperature.cpp
@@ -2237,10 +2237,10 @@ void Temperature::disable_all_heaters() {
     #else
       constexpr uint8_t hindex = 0;
       #define MAX6675_TEMP(I) max6675_temp
-      #if MAX6675_0_IS_MAX31865
-        #define MAX6675_SEL(A,B) A
-      #else
+      #if MAX6675_1_IS_MAX31865
         #define MAX6675_SEL(A,B) B
+      #else
+        #define MAX6675_SEL(A,B) A
       #endif
       #if HEATER_0_USES_MAX6675
         #define MAX6675_WRITE(V)          WRITE(MAX6675_SS_PIN, V)