Minor optimization
diff --git a/Lib/fontTools/ttLib/tables/otBase.py b/Lib/fontTools/ttLib/tables/otBase.py
index 9f6f84d..47b9df4 100644
--- a/Lib/fontTools/ttLib/tables/otBase.py
+++ b/Lib/fontTools/ttLib/tables/otBase.py
@@ -319,8 +319,9 @@
 					item._doneWriting()
 				else:
 					item._doneWriting(internedTables)
-					if item in internedTables:
-						items[i] = item = internedTables[item]
+					internedItem = internedTables.get(item)
+					if internedItem:
+						items[i] = item = internedItem
 					else:
 						internedTables[item] = item
 		self.items = tuple(items)