diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index be759be..89c0c88 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -7,7 +7,7 @@ jobs:
     runs-on: blacksmith-4vcpu-ubuntu-2204
     strategy:
       matrix:
-        python-version: [3.8,3.9,"3.10","3.12"]
+        python-version: ["3.9","3.10","3.11","3.12","3.13","pypy3.10"]
     steps:
       - name: Check out code from GitHub
         uses: actions/checkout@v4
diff --git a/setup.py b/setup.py
index 4755502..1c8c9fc 100644
--- a/setup.py
+++ b/setup.py
@@ -15,12 +15,11 @@
     Development Status :: 5 - Production/Stable
     Programming Language :: Python
     Programming Language :: Python :: 3
-    Programming Language :: Python :: 3.7
-    Programming Language :: Python :: 3.8
     Programming Language :: Python :: 3.9
     Programming Language :: Python :: 3.10
     Programming Language :: Python :: 3.11
     Programming Language :: Python :: 3.12
+    Programming Language :: Python :: 3.13
     Programming Language :: Python :: 3 :: Only
     Programming Language :: Python :: Implementation :: CPython
     Programming Language :: Python :: Implementation :: PyPy
@@ -112,7 +111,7 @@ def run_tests(self):
     platforms=['any'],
     classifiers=classifiers,
     license='BSD',
-    python_requires=">=3.6",
+    python_requires=">=3.9",
     install_requires=[],
     tests_require=reqs('test.txt'),
     cmdclass={'test': pytest},
diff --git a/tox.ini b/tox.ini
index c5e5937..f159e77 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,6 +1,6 @@
 [tox]
 envlist =
-    {pypy3,3.12,3.8,3.9,3.10}-unit
+    {3.9,3.10,3.11,3.12,3.13,pypy3.10}-unit
     flake8
     apicheck
     pydocstyle
@@ -19,10 +19,10 @@ commands = py.test -xv --cov=vine --cov-report=xml --no-cov-on-fail t/unit {posa
 
 basepython =
     flake8,apicheck,linkcheck,pydocstyle: python3.10
-    pypy3: pypy3.10
-    3.8: python3.8
+    pypy3.10: pypy3.10
     3.9: python3.9
     3.10: python3.10
+    3.11: python3.11
     3.12: python3.12
 
 [testenv:apicheck]
diff --git a/vine/synchronization.py b/vine/synchronization.py
index 539a5fc..26cfd85 100644
--- a/vine/synchronization.py
+++ b/vine/synchronization.py
@@ -32,6 +32,7 @@ def all_done():
     Note that you cannot add new promises to a barrier after
     the barrier is fulfilled.
     """
+
     __slots__ = (
         'p', 'args', 'kwargs', '_value', 'size',
         'ready', 'reason', 'cancelled', 'finalized',