diff --git a/pyproject.toml b/pyproject.toml
index 9ed9aa3..b05f17d 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -32,7 +32,7 @@ dependencies = [
     "bw2calc>=2.0.dev13",
     "bw_processing",
     "matrix_utils",
-    "numpy",
+    "numpy<2",
     "scipy",
 ]