diff --git a/dmx.py b/dmx.py
index dbd4be1..b09f574 100644
--- a/dmx.py
+++ b/dmx.py
@@ -51,7 +51,7 @@ class FixtureType:
         else:
             number = value
 
-        return (name, number)
+        return (name, int(number))
 
     def channel(self, name):
         if name not in self._channels:
@@ -60,12 +60,12 @@ class FixtureType:
 
     def range_lookup(self, channel, name, number):
         channel = self.channel(channel)
-        range = channel['range']
-        if isinstance(range, dict):
-            if name not in range:
+        chrange = channel['range']
+        if isinstance(chrange, dict) and (name is not None):
+            if name not in chrange:
                 raise KeyError('Range {} not found'.format(name))
-            (a, b) = range['range']
-            if number < a or number > b:
+            (a, b) = chrange[name]
+            if number < 0 or number > b-1:
                 raise ValueError('DMX value out of range')
             return a + number
         else: