diff --git a/.ci_support/environment-old.yml b/.ci_support/environment-old.yml
index 031d8291..150bd3f4 100644
--- a/.ci_support/environment-old.yml
+++ b/.ci_support/environment-old.yml
@@ -2,7 +2,7 @@ channels:
 - conda-forge
 dependencies:
 - python
-- numpy
+- numpy =1.23.5
 - openmpi =4.1.4
 - cloudpickle =2.0.0
 - mpi4py =3.1.4