diff --git a/tox.ini b/tox.ini
index fb5732f..fcad3c3 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,26 +1,29 @@
 [tox]
 envlist=flake8,mypy,py3
 
 [testenv:py3]
 deps =
   .[testing]
   pytest-cov
 whitelist_externals = mvn
 commands =
   mvn -f java/server/pom.xml compile assembly:single
-  pytest --cov=swh --cov-branch {posargs}
+  pytest --cov={envsitepackagesdir}/swh/graph \
+         {envsitepackagesdir}/swh/graph \
+         --cov-branch {posargs}
+
 
 [testenv:flake8]
 skip_install = true
 deps =
   flake8
 commands =
   {envpython} -m flake8
 
 [testenv:mypy]
 skip_install = true
 deps =
   .[testing]
   mypy
 commands =
   mypy swh