diff --git a/Marlin/Configuration.h b/Marlin/Configuration.h
index 054e90d8d9..f2884c75cb 100644
--- a/Marlin/Configuration.h
+++ b/Marlin/Configuration.h
@@ -1170,6 +1170,12 @@
  * Filament Runout Sensors
  * Mechanical or opto endstops are used to check for the presence of filament.
  *
+ * IMPORTANT: Runout will only trigger if Marlin is aware that a print job is running.
+ * Marlin knows a print job is running when:
+ *  1. Running a print job from media started with M24.
+ *  2. The Print Job Timer has been started with M75.
+ *  3. The heaters were turned on and PRINTJOB_TIMER_AUTOSTART is enabled.
+ *
  * RAMPS-based boards use SERVO3_PIN for the first runout sensor.
  * For other boards you may need to define FIL_RUNOUT_PIN, FIL_RUNOUT2_PIN, etc.
  */