diff --git a/spindle_control.c b/spindle_control.c
index 5dfab0b..813ee8a 100644
--- a/spindle_control.c
+++ b/spindle_control.c
@@ -25,7 +25,10 @@
 
 static uint8_t current_direction;
 static uint16_t current_rpm;
-static uint8_t current_pwm;
+
+#ifdef VARIABLE_SPINDLE
+static uint8_t current_pwm; // Stores the PWM set by the S value
+#endif 
 
 void spindle_init()
 {
@@ -86,12 +89,17 @@ void spindle_run(int8_t direction, uint16_t rpm) {
 	}
 }
 
+#ifdef VARIABLE_SPINDLE
 uint8_t spindle_pwm()
 {
+	// This function can be used by the st_prep_buffer() to calculate what the spindle speed vs travel speed
 	return current_pwm;
 }
 
 void spindle_pwm_update(uint8_t pwm)
 {
+	// This function can be used by the stepper interrupt to set the spindle speed
 	OCR_REGISTER = pwm;
+
 }
+#endif
\ No newline at end of file
diff --git a/spindle_control.h b/spindle_control.h
index 4af96f1..9e4384f 100644
--- a/spindle_control.h
+++ b/spindle_control.h
@@ -27,7 +27,10 @@
 void spindle_init();
 void spindle_run(int8_t direction, uint16_t rpm);
 void spindle_stop();
+
+#ifdef VARIABLE_SPINDLE
 uint8_t spindle_pwm();
 void spindle_pwm_update(uint8_t pwm);
+#endif
 
 #endif