diff --git a/tox.ini b/tox.ini
index dd717bff..72affc86 100644
--- a/tox.ini
+++ b/tox.ini
@@ -18,6 +18,8 @@ setenv =
     mpldev: PIP_EXTRA_INDEX_URL = https://pypi.anaconda.org/scientific-python-nightly-wheels/simple
 changedir = .tmp/{envname}
 description = run tests
+constrain_package_deps =
+    !mpldev-!pytestdev: true
 deps =
     pytest-xdist
     mpl20: matplotlib==2.0.*