diff --git a/build-number.txt b/build-number.txt
index 77afe23..31cf34b 100644
--- a/build-number.txt
+++ b/build-number.txt
@@ -1 +1 @@
-509
+513
diff --git a/src/light_sensor.h b/src/light_sensor.h
index da9f234..cd56d74 100644
--- a/src/light_sensor.h
+++ b/src/light_sensor.h
@@ -10,7 +10,7 @@
 
 // Resolution of the brightness output
 #define LIGHTSENSOR_BITS        12
-#define LIGHTSENSOR_MAX         (1 << LIGHTSENSOR_BITS)
+#define LIGHTSENSOR_MAX         ((1 << LIGHTSENSOR_BITS) - 1)
 
 // 'Forgetting factor' of the rolling brightness average
 #define LIGHTSENSOR_LAMBDA_BITS 2