diff --git a/pyproject.toml b/pyproject.toml
index ccb2a64..dbab66a 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -36,6 +36,7 @@ classifiers = [
 requires-python = ">=3.10"
 dependencies = [
     "attrs",  # todo: bounds?
+    "boltons",  # todo: bounds?
     "cattrs",  # todo: bounds?
     "flopy>=3.7.0",
     "Jinja2>=3.0",