diff --git a/Lib/fontTools/ttLib/tables/otBase.py b/Lib/fontTools/ttLib/tables/otBase.py
index 33454a4bb..c20438ed3 100644
--- a/Lib/fontTools/ttLib/tables/otBase.py
+++ b/Lib/fontTools/ttLib/tables/otBase.py
@@ -237,7 +237,7 @@ class OTTableWriter(object):
 
 	"""Helper class to gather and assemble data for OpenType tables."""
 
-	def __init__(self, globalState, localState=None):
+	def __init__(self, globalState={}, localState=None):
 		self.items = []
 		self.pos = None
 		self.globalState = globalState
diff --git a/Lib/fontTools/ttLib/tables/otBase_test.py b/Lib/fontTools/ttLib/tables/otBase_test.py
index 8496fc7a4..8ab394be2 100644
--- a/Lib/fontTools/ttLib/tables/otBase_test.py
+++ b/Lib/fontTools/ttLib/tables/otBase_test.py
@@ -61,32 +61,32 @@ class OTTableReaderTest(unittest.TestCase):
 
 class OTTableWriterTest(unittest.TestCase):
     def test_writeShort(self):
-        writer = OTTableWriter(globalState={})
+        writer = OTTableWriter()
         writer.writeShort(-12345)
         self.assertEqual(writer.getData(), deHexStr("CF C7"))
 
     def test_writeLong(self):
-        writer = OTTableWriter(globalState={})
+        writer = OTTableWriter()
         writer.writeLong(-12345678)
         self.assertEqual(writer.getData(), deHexStr("FF 43 9E B2"))
 
     def test_writeUInt8(self):
-        writer = OTTableWriter(globalState={})
+        writer = OTTableWriter()
         writer.writeUInt8(0xBE)
         self.assertEqual(writer.getData(), deHexStr("BE"))
 
     def test_writeUShort(self):
-        writer = OTTableWriter(globalState={})
+        writer = OTTableWriter()
         writer.writeUShort(0xBEEF)
         self.assertEqual(writer.getData(), deHexStr("BE EF"))
 
     def test_writeUInt24(self):
-        writer = OTTableWriter(globalState={})
+        writer = OTTableWriter()
         writer.writeUInt24(0xBEEF77)
         self.assertEqual(writer.getData(), deHexStr("BE EF 77"))
 
     def test_writeULong(self):
-        writer = OTTableWriter(globalState={})
+        writer = OTTableWriter()
         writer.writeULong(0xBEEFCAFE)
         self.assertEqual(writer.getData(), deHexStr("BE EF CA FE"))
 
diff --git a/Lib/fontTools/ttLib/tables/otConverters_test.py b/Lib/fontTools/ttLib/tables/otConverters_test.py
index ef550e242..4787e236b 100644
--- a/Lib/fontTools/ttLib/tables/otConverters_test.py
+++ b/Lib/fontTools/ttLib/tables/otConverters_test.py
@@ -25,7 +25,7 @@ class GlyphIDTest(unittest.TestCase):
         self.assertEqual(reader.pos, 2)
 
     def test_write(self):
-        writer = OTTableWriter(globalState={})
+        writer = OTTableWriter()
         self.converter.write(writer, self.font, {}, "B")
         self.assertEqual(writer.getData(), deHexStr("0002"))
 
@@ -44,7 +44,7 @@ class NameIDTest(unittest.TestCase):
         self.assertEqual(self.converter.read(reader, font, {}), 0x123)
 
     def test_write(self):
-        writer = OTTableWriter(globalState={})
+        writer = OTTableWriter()
         self.converter.write(writer, self.makeFont(), {}, 0x123)
         self.assertEqual(writer.getData(), deHexStr("0123"))