diff --git a/spack.yaml b/spack.yaml
index 8b137891791fe96927ad78e64b0aad7bded08bdc..cf5d26ef2bc8a305c54aee68d3a4224941af2121 100644
--- a/spack.yaml
+++ b/spack.yaml
@@ -1 +1,7 @@
-
+spack:
+  specs:
+    - nest +python +gsl +mpi ^py-scipy@:1.6.999 %gcc@10.3.0
+    - arbor +mpi %gcc@10.3.0
+    - neuron +mpi %gcc@10.3.0
+    # BrainScaleS (plus some constraining)
+    - visionary-dls-core ^py-setuptools-scm+toml ^python@3.8.0:3.8.999 ^binutils+ld ^py-astroid@2.5.6:2.6.999 ^py-scipy@:1.6.999 %gcc@10.3.0