diff --git a/src/stc15_dusk.c b/src/stc15_dusk.c
index 0d3cb5a..a7b70d2 100644
--- a/src/stc15_dusk.c
+++ b/src/stc15_dusk.c
@@ -1,5 +1,7 @@
 #include "stc15_dusk.h"
 
+#define STC15_LIGHT_THRESHOLD 219
+
 unsigned char dusk_value = 0;
 
 void nop_wait() {
@@ -25,6 +27,6 @@ void stc15_update_light_state() {
 }
 
 unsigned char stc15_is_low_light() {
-  return dusk_value > 219;
+  return dusk_value > STC15_LIGHT_THRESHOLD;
 }
 
diff --git a/src/stc15_dusk.h b/src/stc15_dusk.h
index 7499d2e..648bc4d 100644
--- a/src/stc15_dusk.h
+++ b/src/stc15_dusk.h
@@ -15,7 +15,6 @@
 
 void stc15_dusk_init();
 
-/* should be called periodically */
 void stc15_update_light_state();
 
 unsigned char stc15_is_low_light();