diff --git a/devtools/conda-envs/test_env.yaml b/devtools/conda-envs/test_env.yaml
index a4703e12..d261e15d 100644
--- a/devtools/conda-envs/test_env.yaml
+++ b/devtools/conda-envs/test_env.yaml
@@ -5,7 +5,7 @@ channels:
 dependencies:
   - python
   - cython
-  - numpy
+  - numpy<2
   - scipy
   - h5py
   - pyyaml