diff --git a/CHANGELOG.md b/CHANGELOG.md
index 8a4b07b..1f2e696 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,11 @@
 # Changelog
 
+## 4.0.1
+
+Requires `python-introspect>=0.3.0,<0.4` (was `<0.3`). ObjectState does not call
+python-introspect's JSON codec (`to_jsonable`, `dataclass_from_mapping`), so nothing
+it stores or sends changes form.
+
 ## 4.0.0
 
 The global config has one holder (#56). While a state whose object is of the
diff --git a/pyproject.toml b/pyproject.toml
index 88df81c..9061cdf 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -26,7 +26,7 @@ keywords = ["configuration", "dataclass", "lazy", "inheritance", "contextvars",
 dependencies = [
     "dill>=0.4.0",
     "pycodify>=0.2.0,<0.3",
-    "python-introspect>=0.2.0,<0.3",
+    "python-introspect>=0.3.0,<0.4",
 ]
 
 [project.optional-dependencies]
diff --git a/src/objectstate/__init__.py b/src/objectstate/__init__.py
index 62005b4..5e7ef44 100644
--- a/src/objectstate/__init__.py
+++ b/src/objectstate/__init__.py
@@ -206,7 +206,7 @@
     'ObjectStateEditSession',
 ]
 
-__version__ = "4.0.0"
+__version__ = "4.0.1"
 __author__ = 'OpenHCS Team'
 __description__ = 'Generic configuration framework for lazy dataclass resolution'