diff --git a/tox.ini b/tox.ini
index 8041abb07..87d419890 100644
--- a/tox.ini
+++ b/tox.ini
@@ -20,19 +20,22 @@ envlist =
 
 [testenv]
 commands =
-    {env:_PYTEST_TOX_COVERAGE_RUN:} pytest --lsof {posargs}
+    {env:_PYTEST_TOX_COVERAGE_RUN:} pytest {env:_PYTEST_TOX_ARGS:} {posargs}
     coverage: coverage combine
     coverage: coverage report
 passenv = USER USERNAME COVERAGE_* TRAVIS PYTEST_ADDOPTS
 setenv =
+    _PYTEST_TOX_ARGS=--lsof
     # Configuration to run with coverage similar to Travis/Appveyor, e.g.
     # "tox -e py37-coverage".
     coverage: _PYTEST_TOX_COVERAGE_RUN=coverage run -m
     coverage: _PYTEST_TOX_EXTRA_DEP=coverage-enable-subprocess
     coverage: COVERAGE_FILE={toxinidir}/.coverage
     coverage: COVERAGE_PROCESS_START={toxinidir}/.coveragerc
+    xdist: _PYTEST_TOX_ARGS={env:_PYTEST_TOX_ARGS:-n auto}
 extras = testing
 deps =
+    xdist: pytest-xdist>=1.13
     {env:_PYTEST_TOX_EXTRA_DEP:}
 
 [testenv:py27-subprocess]
@@ -50,22 +53,6 @@ basepython = python3
 deps = pre-commit>=1.11.0
 commands = pre-commit run --all-files --show-diff-on-failure
 
-[testenv:py27-xdist]
-extras = testing
-deps =
-    {[testenv]deps}
-    pytest-xdist>=1.13
-commands =
-    {env:_PYTEST_TOX_COVERAGE_RUN:} pytest -n auto {posargs}
-
-[testenv:py37-xdist]
-# NOTE: copied from above due to https://github.com/tox-dev/tox/issues/706.
-extras = testing
-deps =
-    {[testenv]deps}
-    pytest-xdist>=1.13
-commands = {[testenv:py27-xdist]commands}
-
 [testenv:py27-pexpect]
 platform = linux|darwin
 deps =