diff --git a/tox.ini b/tox.ini
index 6f1a4d9..c81b72a 100644
--- a/tox.ini
+++ b/tox.ini
@@ -55,7 +55,7 @@ commands =
 [testenv:install]
 description = Install locally built, unsigned snap on system.
 commands =
-    bash -c "sudo snap install {toxinidir}/spack_*_amd64.snap --dangerous"
+    bash -c "sudo snap install {toxinidir}/spack_*_amd64.snap --dangerous --classic"
 
 [testenv:unit]
 description = Run unit tests