diff --git a/pyproject.toml b/pyproject.toml
index fb7ce54..2c2e444 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -27,6 +27,7 @@ classifiers = [
 dependencies = [
     "numpy >=1.21.0",
     "pygame>=2.1.0",
+    "pettingzoo>=1.23.1",
 ]
 dynamic = ["version"]