Index: apptools-5.2.0/apptools/persistence/state_pickler.py
===================================================================
--- apptools-5.2.0.orig/apptools/persistence/state_pickler.py
+++ apptools-5.2.0/apptools/persistence/state_pickler.py
@@ -393,11 +393,14 @@ class StatePickler:
             args = value.__getinitargs__()
 
         # Get the object state.
+        state = None
         if hasattr(value, "__get_pure_state__"):
             state = value.__get_pure_state__()
         elif hasattr(value, "__getstate__"):
+            # Note that __getstate__() may return None in Python >= 3.11
             state = value.__getstate__()
-        else:
+
+        if state is None:
             state = value.__dict__
 
         state.pop("__traits_version__", None)
Index: apptools-5.2.0/docs/releases/upcoming/328.bugfix.rst
===================================================================
--- /dev/null
+++ apptools-5.2.0/docs/releases/upcoming/328.bugfix.rst
@@ -0,0 +1 @@
+Fix StatePickler for Python 3.11. (#328)
\ No newline at end of file