diff --git a/bindep.txt b/bindep.txt
new file mode 100644
index 000000000..5774e51c1
--- /dev/null
+++ b/bindep.txt
@@ -0,0 +1,2 @@
+graphviz [!platform:gentoo]
+media-gfx/graphviz [platform:gentoo]
diff --git a/tox.ini b/tox.ini
index 4d249389c..90b34bb56 100644
--- a/tox.ini
+++ b/tox.ini
@@ -78,6 +78,7 @@ commands = sphinx-build -a -E -W -d releasenotes/build/doctrees -b html releasen
 
 [testenv:api-ref]
 basepython = python3
+deps = -r{toxinidir}/doc/requirements.txt
 commands =
   sphinx-build -W -b html -d api-ref/build/doctrees api-ref/source api-ref/build/html