Minor

Followup for 6e556aafc3be5ccf48a01d8113313abd2a633ba6.
diff --git a/Lib/fontTools/ttLib/tables/otBase.py b/Lib/fontTools/ttLib/tables/otBase.py
index 7689912..0ee5141 100644
--- a/Lib/fontTools/ttLib/tables/otBase.py
+++ b/Lib/fontTools/ttLib/tables/otBase.py
@@ -744,7 +744,7 @@
 	
 	"""Given a format code, this object convert ValueRecords."""
 
-	def __init__(self, valueFormat=0):
+	def __init__(self, valueFormat):
 		format = []
 		for mask, name, isDevice, signed in valueRecordFormat:
 			if valueFormat & mask: