diff --git a/Lib/fontTools/varLib/__init__.py b/Lib/fontTools/varLib/__init__.py
index 342d256c5..7bb2bbcd0 100644
--- a/Lib/fontTools/varLib/__init__.py
+++ b/Lib/fontTools/varLib/__init__.py
@@ -538,14 +538,14 @@ def build(designspace_filename, master_finder=lambda s:s):
 	for obj in masters+instances:
 		obj_name = obj.get('name', obj.get('stylename', ''))
 		loc = obj['location']
-		for name in loc.keys():
-			assert name in axes, "Location axis '%s' unknown for '%s'." % (name, obj_name)
+		for axis_name in loc.keys():
+			assert axis_name in axes, "Location axis '%s' unknown for '%s'." % (axis_name, obj_name)
 		for axis_name,axis in axes.items():
 			if axis_name not in loc:
 				loc[axis_name] = axis.default
 			else:
 				v = axis.map_backward(loc[axis_name])
-				assert axis.minimum <= v <= axis.maximum, "Location for axis '%s' (mapped to %s) out of range for '%s' [%s..%s]" % (name, v, obj_name, axis.minimum, axis.maximum)
+				assert axis.minimum <= v <= axis.maximum, "Location for axis '%s' (mapped to %s) out of range for '%s' [%s..%s]" % (axis_name, v, obj_name, axis.minimum, axis.maximum)
 
 
 	# Normalize master locations