diff --git a/spack.yaml b/spack.yaml
index 7dd65f5aa45da1d6af5ad0d9da25ac2fa164e486..b884ecbe1f56d490c4a5451ed69cc22a1a2bdb4a 100644
--- a/spack.yaml
+++ b/spack.yaml
@@ -2,8 +2,9 @@ spack:
   specs:
     # system
     - autoconf@2.70 %gcc@10.3.0
+    - which %gcc@10.3.0
     # Notebook
-    - py-jupyter ^autoconf@2.70 %gcc@10.3.0
+    - py-jupyter %gcc@10.3.0
     - py-ipython %gcc@10.3.0
     - py-ipykernel %gcc@10.3.0
     - py-notebook %gcc@10.3.0