diff --git a/tox.ini b/tox.ini
index db4bdd4..b96f936 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,27 +1,28 @@
 [tox]
 envlist=flake8,mypy,py3
 
 [testenv]
 extras =
   testing
 deps =
   pytest-cov
+  dev: pdbpp
 commands =
   pytest --cov={envsitepackagesdir}/swh/loader/svn \
       {envsitepackagesdir}/swh/loader/svn \
       --cov-branch  {posargs}
 
 [testenv:flake8]
 skip_install = true
 deps =
   flake8
 commands =
   {envpython} -m flake8
 
 [testenv:mypy]
 extras =
   testing
 deps =
   mypy
 commands =
   mypy swh