diff --git a/pyproject.toml b/pyproject.toml
index ae44f48..64cbc0f 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -39,7 +39,7 @@ classifiers = [
 readme = "README.md"
 
 dependencies = [
-    "numpy>=1.9",
+    "numpy>=1.9, <2",
     "scipy>=0.16",
     "pandas>1.5",
     "h5py>=2.5",