diff --git a/pyproject.toml b/pyproject.toml
index 1d2087ca..541b310a 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -45,7 +45,7 @@ classifiers = [
 ]
 dependencies = [
     "gymnasium",
-    "numpy",
+    "numpy<2.0.0",
 ]
 
 [project.urls]