diff --git a/grbl/defaults.h b/grbl/defaults.h
index 27fa196..f58d000 100644
--- a/grbl/defaults.h
+++ b/grbl/defaults.h
@@ -115,7 +115,7 @@
   #define DEFAULT_ARC_TOLERANCE 0.002       // mm
   #define DEFAULT_REPORT_INCHES 0           // false
   #define DEFAULT_INVERT_ST_ENABLE 0        // false
-  #define DEFAULT_INVERT_LIMIT_PINS 1       // true
+  #define DEFAULT_INVERT_LIMIT_PINS 1       // true for microswitches / false for optical sensors
   #define DEFAULT_SOFT_LIMIT_ENABLE 1       // true
   #define DEFAULT_HARD_LIMIT_ENABLE 0       // false
   #define DEFAULT_INVERT_PROBE_PIN 0        // false