diff --git a/.travis.yml b/.travis.yml
index e215f2f..0f0a6be 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -54,6 +54,9 @@ jobs:
     - python: '3.8'
       env:
         - TOXENV=py38,report,codecov
+    - python: 'pypy3'
+      env:
+        - TOXENV=pypy3,report,codecov
     - python: '3.8'
       env:
         - TOXENV=doc
diff --git a/tests/test_make.py b/tests/test_make.py
index 68014b2..87ce245 100644
--- a/tests/test_make.py
+++ b/tests/test_make.py
@@ -396,6 +396,11 @@ class B:
     assert_dump_load(schema=schema, loaded=loaded, dumped=dumped)
 
 
+# 3.6.9 is known to work, 3.6.1 is known to fail, not sure attrs vs. dataclasses
+@pytest.mark.skipif(
+    condition=sys.implementation.name == "pypy" and sys.version_info < (3, 6, 9),
+    reason="Forward references and string annotations are broken.",
+)
 def test_forward_reference_module_scope():
     """Run the forward reference test at global scope."""
 
diff --git a/tox.ini b/tox.ini
index 2cd3330..bf696ba 100644
--- a/tox.ini
+++ b/tox.ini
@@ -16,14 +16,13 @@ basepython =
     py38: {env:TOXPYTHON:python3.8}
     {doc,spell,bootstrap,clean,check,report,codecov}: {env:TOXTOOLPYTHON:python3.8}
 setenv =
-    PYTHONPATH={toxinidir}/tests
     PYTHONUNBUFFERED=yes
 passenv =
     *
 deps =
     -r {toxinidir}/test-requirements.txt
 commands =
-    pytest {posargs:--cov --cov-report=term-missing -vv --doctest-modules tests}
+    {envbindir}/pytest {posargs:--cov --cov-report=term-missing -vv --doctest-modules tests}
 
 [testenv:bootstrap]
 deps =
@@ -31,54 +30,54 @@ deps =
     matrix
 skip_install = true
 commands =
-    python ci/bootstrap.py
+    {envpython} ci/bootstrap.py
 
 [testenv:check]
 deps =
      -r {toxinidir}/dev-requirements.txt
 skip_install = true
 commands =
-    python setup.py check --strict --metadata --restructuredtext
-    check-manifest {toxinidir}
-    black --check {toxinidir}
-    isort --verbose --check-only --diff --recursive src tests setup.py
+    {envpython} setup.py check --strict --metadata --restructuredtext
+    {envbindir}/check-manifest {toxinidir}
+    {envbindir}/black --check {toxinidir}
+    {envbindir}/isort --verbose --check-only --diff --recursive src tests setup.py
 
 [testenv:spell]
 setenv =
     SPELLCHECK=1
 commands =
-    sphinx-build -b spelling docs dist/docs
+    {envbindir}/sphinx-build -b spelling docs dist/docs
 skip_install = true
 deps =
     -r{toxinidir}/docs/requirements.txt
-    sphinxcontrib-spelling
-    pyenchant
+    {envbindir}/sphinxcontrib-spelling
+    {envbindir}/pyenchant
 
 [testenv:doc]
 deps =
     -r{toxinidir}/docs/requirements.txt
 
 commands =
-    sphinx-apidoc -o docs/reference src/desert
-    pytest --doctest-modules --doctest-glob=*.rst src docs
-    sphinx-build {posargs:-E} -b html docs dist/docs
-    sphinx-build -b linkcheck docs dist/docs
+    {envbindir}/sphinx-apidoc -o docs/reference src/desert
+    {envbindir}/pytest --doctest-modules --doctest-glob=*.rst src docs
+    {envbindir}/sphinx-build {posargs:-E} -b html docs dist/docs
+    {envbindir}/sphinx-build -b linkcheck docs dist/docs
 
 [testenv:codecov]
 deps =
     codecov
 skip_install = true
 commands =
-    coverage xml --ignore-errors
-    codecov []
+    {envbindir}/coverage xml --ignore-errors
+    {envbindir}/codecov []
 
 [testenv:report]
 deps = coverage
        cuvner
 skip_install = true
 commands =
-    coverage report
-    coverage html
+    {envbindir}/coverage report
+    {envbindir}/coverage html
 
 
 [testenv:clean]