diff --git a/pyproject.toml b/pyproject.toml
index 3b732340..233be6c2 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -75,7 +75,7 @@ include = ["hed*"]
 namespaces = false
 
 [tool.setuptools.package-data]
-hed = ["schema/schema_data/*.xml", "resources/*.png"]
+hed = ["schema/schema_data/*.xml", "resources/*.png", "validator/util/class_regex.json"]
 
 [tool.codespell]
 skip = '*.git,*.pdf,*.svg,versioneer.py,venv*,*.tsv,*.yaml,*.yml,*.json,*.rdf,*.jsonld,spec_tests,,*.xml,*.mediawiki,*.omn,*.toml'