diff --git a/.travis.yml b/.travis.yml
index 3002df6..768f7dc 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,31 +1,28 @@
 language: python
-sudo: false
-dist: trusty
+dist: focal
 
 matrix:
   include:
     # These are quick and often catch errors, so list them first
-    - python: 3.6
+    - python: 3.8
       env: CHECK_DOCS=1
-    - python: 3.6
+    - python: 3.8
       env: CHECK_FORMATTING=1
-    # The pypy tests are slow, so list them early
-    - python: pypy3.5
+    # The pypy tests are slow, so we list them first
+    - python: pypy3.6-7.2.0
+      dist: bionic
+    - language: generic
+      env: PYPY_NIGHTLY_BRANCH=py3.6
     # Uncomment if you want to test on pypy nightly:
     # - language: generic
     #   env: USE_PYPY_NIGHTLY=1
-    - python: 3.5.0
-    - python: 3.5.2
-    - python: 3.6
+    - python: 3.6-dev
     # As of 2018-07-05, Travis's 3.7 and 3.8 builds only work if you
     # use dist: xenial AND sudo: required
     # See: https://github.com/python-trio/trio/pull/556#issuecomment-402879391
-    - python: 3.7
-      dist: xenial
-      sudo: required
+    - python: 3.7-dev
     - python: 3.8-dev
-      dist: xenial
-      sudo: required
+    - python: 3.9-dev
 
 script:
   - ci/travis.sh
diff --git a/ci/rtd-requirements.in b/ci/rtd-requirements.in
new file mode 100644
index 0000000..67898ba
--- /dev/null
+++ b/ci/rtd-requirements.in
@@ -0,0 +1,4 @@
+# RTD is currently installing 1.5.3, which has a bug in :lineno-match:
+sphinx >= 1.6.1
+sphinx_rtd_theme
+sphinxcontrib-trio
diff --git a/ci/rtd-requirements.txt b/ci/rtd-requirements.txt
index 67898ba..8008227 100644
--- a/ci/rtd-requirements.txt
+++ b/ci/rtd-requirements.txt
@@ -1,4 +1,35 @@
-# RTD is currently installing 1.5.3, which has a bug in :lineno-match:
-sphinx >= 1.6.1
-sphinx_rtd_theme
-sphinxcontrib-trio
+#
+# This file is autogenerated by pip-compile
+# To update, run:
+#
+#    pip-compile --output-file=rtd-requirements.txt rtd-requirements.in
+#
+alabaster==0.7.12         # via sphinx
+babel==2.8.0              # via sphinx
+certifi==2020.6.20        # via requests
+chardet==3.0.4            # via requests
+docutils==0.16            # via sphinx
+idna==2.10                # via requests
+imagesize==1.2.0          # via sphinx
+jinja2==2.11.2            # via sphinx
+markupsafe==1.1.1         # via jinja2
+packaging==20.4           # via sphinx
+pygments==2.6.1           # via sphinx
+pyparsing==2.4.7          # via packaging
+pytz==2020.1              # via babel
+requests==2.24.0          # via sphinx
+six==1.15.0               # via packaging
+snowballstemmer==2.0.0    # via sphinx
+sphinx-rtd-theme==0.5.0   # via -r rtd-requirements.in
+sphinx==3.2.1             # via -r rtd-requirements.in, sphinx-rtd-theme, sphinxcontrib-trio
+sphinxcontrib-applehelp==1.0.2  # via sphinx
+sphinxcontrib-devhelp==1.0.2  # via sphinx
+sphinxcontrib-htmlhelp==1.0.3  # via sphinx
+sphinxcontrib-jsmath==1.0.1  # via sphinx
+sphinxcontrib-qthelp==1.0.3  # via sphinx
+sphinxcontrib-serializinghtml==1.1.4  # via sphinx
+sphinxcontrib-trio==1.1.2  # via -r rtd-requirements.in
+urllib3==1.25.10          # via requests
+
+# The following packages are considered to be unsafe in a requirements file:
+# setuptools
diff --git a/setup.py b/setup.py
index 3195c92..034e4dc 100644
--- a/setup.py
+++ b/setup.py
@@ -21,9 +21,11 @@
         "attrs",
     ],
     keywords=[
-        "async", "scheduler", "trio",
+        "async",
+        "scheduler",
+        "trio",
     ],
-    python_requires=">=3.5",
+    python_requires=">=3.6",
     classifiers=[
         "License :: OSI Approved :: MIT License",
         "License :: OSI Approved :: Apache Software License",
diff --git a/test-requirements.in b/test-requirements.in
new file mode 100644
index 0000000..9955dec
--- /dev/null
+++ b/test-requirements.in
@@ -0,0 +1,2 @@
+pytest
+pytest-cov
diff --git a/test-requirements.txt b/test-requirements.txt
index 9955dec..c409c63 100644
--- a/test-requirements.txt
+++ b/test-requirements.txt
@@ -1,2 +1,18 @@
-pytest
-pytest-cov
+#
+# This file is autogenerated by pip-compile
+# To update, run:
+#
+#    pip-compile --output-file=test-requirements.txt test-requirements.in
+#
+attrs==20.1.0             # via pytest
+coverage==5.2.1           # via pytest-cov
+iniconfig==1.0.1          # via pytest
+more-itertools==8.5.0     # via pytest
+packaging==20.4           # via pytest
+pluggy==0.13.1            # via pytest
+py==1.9.0                 # via pytest
+pyparsing==2.4.7          # via packaging
+pytest-cov==2.10.1        # via -r test-requirements.in
+pytest==6.0.1             # via -r test-requirements.in, pytest-cov
+six==1.15.0               # via packaging
+toml==0.10.1              # via pytest
diff --git a/trimeter/_impl.py b/trimeter/_impl.py
index 484a022..480f6ca 100644
--- a/trimeter/_impl.py
+++ b/trimeter/_impl.py
@@ -56,7 +56,8 @@ def new_state(self):
 class MaxState:
     def __init__(self, max_meter):
         self.sem = trio.Semaphore(
-            initial_value=max_meter.max_at_once, max_value=max_meter.max_at_once
+            initial_value=max_meter.max_at_once,
+            max_value=max_meter.max_at_once
         )
 
     async def wait_task_can_start(self):
@@ -73,7 +74,9 @@ def notify_task_finished(self):
 @attr.s(frozen=True)
 class TokenBucketMeter:
     max_per_second = attr.ib(converter=float, validator=_check_positive)
-    max_burst = attr.ib(default=1, converter=operator.index, validator=_check_positive)
+    max_burst = attr.ib(
+        default=1, converter=operator.index, validator=_check_positive
+    )
 
     def __attrs_post_init__(self):
         _check_positive(self, "max_per_second", self.max_per_second)
@@ -121,9 +124,7 @@ def notify_task_finished(self):
 
 
 # XX should we have a special-case to allow KeyboardInterrupt to pass through?
-async def _worker(
-        async_fn, value, index, config
-):
+async def _worker(async_fn, value, index, config):
     if config.capture_outcome:
         result = await outcome.acapture(async_fn, value)
     else:
@@ -203,7 +204,6 @@ async def run_on_each(
             await send_to.aclose()
 
 
-
 @asynccontextmanager
 @async_generator
 async def amap(
diff --git a/trimeter/_tests/conftest.py b/trimeter/_tests/conftest.py
index 25c5453..e51a6a2 100644
--- a/trimeter/_tests/conftest.py
+++ b/trimeter/_tests/conftest.py
@@ -5,6 +5,7 @@
 import pytest
 from trio.testing import MockClock, trio_test
 
+
 @pytest.fixture
 def mock_clock():
     return MockClock()
diff --git a/trimeter/_tests/test_basics.py b/trimeter/_tests/test_basics.py
index af6caba..7fd470c 100644
--- a/trimeter/_tests/test_basics.py
+++ b/trimeter/_tests/test_basics.py
@@ -2,6 +2,7 @@
 import trio
 from trimeter import run_on_each, amap, run_all
 
+
 # Just the most basic smoke test of the three functions
 async def test_basics():
     ran_on = []
@@ -20,9 +21,11 @@ async def afn(value):
             results.append(result)
         assert sorted(results) == [2, 3, 4]
 
-    results = await run_all([
-        partial(afn, 10),
-        partial(afn, 11),
-        partial(afn, 12),
-    ])
+    results = await run_all(
+        [
+            partial(afn, 10),
+            partial(afn, 11),
+            partial(afn, 12),
+        ]
+    )
     assert results == [11, 12, 13]