diff --git a/adafruit_ws2801.py b/adafruit_ws2801.py
index c8b0cd4..094879f 100644
--- a/adafruit_ws2801.py
+++ b/adafruit_ws2801.py
@@ -195,7 +195,7 @@ def show(self):
         buf = self._buf
         if self.brightness < 1.0:
             buf = bytearray(len(self._buf))
-            for i in range(self._n):
+            for i in range(len(self._buf)):
                 buf[i] = int(self._buf[i] * self._brightness)
 
         if self._spi: