diff --git a/python/CHANGELOG.rst b/python/CHANGELOG.rst
index 3a81b2aa1c..342e06115f 100644
--- a/python/CHANGELOG.rst
+++ b/python/CHANGELOG.rst
@@ -7,9 +7,12 @@
 - Add ``__repr__`` for variants to return a string representation of the raw data
   without spewing megabytes of text (:user:`chriscrsmith`, :pr:`2695`, :issue:`2694`)
 
-- Add ``keep_rows`` method to table classes to support efficient in-place
-  table subsetting (:user:`jeromekelleher`, :pr:`2700`)
+**Breaking Changes**
+
+- Printing ``tskit.MetadataSchema(schema=None)`` now shows ``"Null_schema"`` rather
+  than ``None``, to avoid confusion (:user:`hyanwong`, :pr:`2720`)
 
+  
 --------------------
 [0.5.4] - 2023-01-13
 --------------------
diff --git a/python/tests/test_tables.py b/python/tests/test_tables.py
index b6d207e2e0..570c5a43bc 100644
--- a/python/tests/test_tables.py
+++ b/python/tests/test_tables.py
@@ -1333,9 +1333,8 @@ def test_metadata_schema(self, table_5row):
             table2.metadata_schema = tskit.MetadataSchema({"codec": "json"})
             with pytest.raises(
                 AssertionError,
-                match=f"{type(table_5row).__name__} metadata schemas differ: self=None "
-                f"other=OrderedDict([('codec', "
-                "'json')])",
+                match=f"{type(table_5row).__name__} metadata schemas differ: "
+                "self=Null_schema other=OrderedDict([('codec', 'json')])",
             ):
                 table_5row.assert_equals(table2)
             table_5row.assert_equals(table2, ignore_metadata=True)
@@ -4032,7 +4031,7 @@ def test_metadata_schema(self, t1, t2):
             AssertionError,
             match=re.escape(
                 "Metadata schemas differ: self=OrderedDict([('codec', 'json')]) "
-                "other=None"
+                "other=Null_schema"
             ),
         ):
             t1.assert_equals(t2)
@@ -4081,7 +4080,7 @@ def test_ignore_metadata(self, t1, t2, table_name):
                 AssertionError,
                 match=re.escape(
                     f"{type(table).__name__} metadata schemas differ: "
-                    f"self=OrderedDict([('codec', 'json')]) other=None"
+                    f"self=OrderedDict([('codec', 'json')]) other=Null_schema"
                 ),
             ):
                 t1.assert_equals(t2)
@@ -4142,7 +4141,7 @@ def test_ignore_reference_sequence(self, t1, t2):
             AssertionError,
             match=re.escape(
                 "Metadata schemas differ: "
-                "self=OrderedDict([('codec', 'json')]) other=None"
+                "self=OrderedDict([('codec', 'json')]) other=Null_schema"
             ),
         ):
             t1.assert_equals(t2)
diff --git a/python/tskit/metadata.py b/python/tskit/metadata.py
index b4c978d51c..78e6b97269 100644
--- a/python/tskit/metadata.py
+++ b/python/tskit/metadata.py
@@ -1,6 +1,6 @@
 # MIT License
 #
-# Copyright (c) 2020-2022 Tskit Developers
+# Copyright (c) 2020-2023 Tskit Developers
 #
 # Permission is hereby granted, free of charge, to any person obtaining a copy
 # of this software and associated documentation files (the "Software"), to deal
@@ -654,7 +654,10 @@ def __repr__(self) -> str:
         return self._string
 
     def __str__(self) -> str:
-        return pprint.pformat(self._schema)
+        if self._schema is None:
+            return "Null_schema"
+        else:
+            return pprint.pformat(self._schema)
 
     def __eq__(self, other) -> bool:
         return self._string == other._string