diff --git a/adafruit_dotstar.py b/adafruit_dotstar.py
index 1a3555b..27e5977 100755
--- a/adafruit_dotstar.py
+++ b/adafruit_dotstar.py
@@ -157,7 +157,7 @@ def _set_item(self, index, value):
         if isinstance(value, int):
             rgb = (value >> 16, (value >> 8) & 0xff, value & 0xff)
 
-        if len(value) == 4:
+        if len(rgb) == 4:
             brightness = value[3]
             # Ignore value[3] below.
         else: