diff --git a/pyproject.toml b/pyproject.toml
index 8242013..52d5083 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -47,6 +47,11 @@ dependencies = [
         "WebHelpers2",
         "WuttJamaican[db]>=0.28.1",
         "zope.sqlalchemy>=1.5",
+
+        # nb. this must be pinned for now, until pyramid can remove
+        # its dependency on pkg_resources.
+        # cf. https://github.com/Pylons/pyramid/issues/3731
+        "setuptools<81",
 ]