diff --git a/spack.yaml b/spack.yaml
index 427ba40aabbf041e276a0fe25534e111c4a3e98e..498720ff5015bc6a1c1c9307f0bc1625d5a5cb7c 100644
--- a/spack.yaml
+++ b/spack.yaml
@@ -19,11 +19,11 @@ spack:
     - gcc@10.3.0 os=centos7
   - pkgs:
     # some EBRAINS-related simulators
-    - py-numpy ^python@3.8.10 
-    - py-scipy ^python@3.8.10 
+    #- py-numpy ^python@3.8.10 
+    #- py-scipy ^python@3.8.10 
     #- py-pip ^python@3.8.10 
     #- nest +gsl +python ^python@3.8.10 %gcc@9.3.1
-    #- arbor ^python@3.8.10
+    - arbor
 
     #- nest +gsl +mpi ^py-scipy@:1.6.999
     #- arbor +mpi