diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
new file mode 100644
index 0000000..0e53464
--- /dev/null
+++ b/.github/workflows/tests.yml
@@ -0,0 +1,42 @@
+name: tests
+
+on:
+  push:
+    branches: ["master"]
+  pull_request:
+    branches: ["master"]
+
+jobs:
+  tests:
+    name: "Python ${{ matrix.python-version }} ${{ matrix.os }}"
+    runs-on: ${{ matrix.os }}
+
+    strategy:
+      matrix:
+        python-version: ["2.7", "3.6", "3.7", "3.8", "3.9", "3.10"]
+        os: [ubuntu-latest, macos-latest, windows-latest]
+        exclude:
+          - os: windows-latest
+            python-version: "2.7"
+      fail-fast: false
+
+    steps:
+      - uses: "actions/checkout@v2"
+        with:
+          submodules: true
+      - uses: "actions/setup-python@v2"
+        with:
+          python-version: "${{ matrix.python-version }}"
+      - name: "Install dependencies"
+        run: |
+          python -VV
+          python -m site
+          python -m pip install --upgrade pip setuptools wheel
+          python -m pip install --upgrade virtualenv tox tox-gh-actions
+          python -m pip install --upgrade cython
+
+      - name: "Rebuild CPP files using Cython"
+        run: "./update_cpp.sh"
+
+      - name: "Run tox targets for ${{ matrix.python-version }}"
+        run: "python -m tox"
\ No newline at end of file
diff --git a/setup.py b/setup.py
index 16a2dc8..db92a8e 100755
--- a/setup.py
+++ b/setup.py
@@ -30,10 +30,11 @@
         'Programming Language :: Python :: 2',
         'Programming Language :: Python :: 2.7',
         'Programming Language :: Python :: 3',
-        'Programming Language :: Python :: 3.5',
         'Programming Language :: Python :: 3.6',
         'Programming Language :: Python :: 3.7',
         'Programming Language :: Python :: 3.8',
+        'Programming Language :: Python :: 3.9',
+        'Programming Language :: Python :: 3.10',
         'Programming Language :: Python :: Implementation :: CPython',
         'Topic :: Software Development :: Libraries :: Python Modules',
         'Topic :: Scientific/Engineering :: Information Analysis',
diff --git a/src/dawg.pyx b/src/dawg.pyx
index 6dba921..37258d9 100644
--- a/src/dawg.pyx
+++ b/src/dawg.pyx
@@ -569,7 +569,7 @@ cdef class BytesDAWG(CompletionDAWG):
                 self._completer.length(),
                 b64_decoder_storage
             )
-            results.push_back(string(b64_decoder_storage, key_len))
+            results.push_back(string(<char*>b64_decoder_storage, key_len))
 
         return results
 
diff --git a/tox.ini b/tox.ini
index 6f12e09..4028884 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,14 +1,23 @@
 [tox]
-envlist = py27,py35,py35-locale,py36,py37,py38
+envlist = py27,py36,py36-locale,py37,py38,py39,py310
+
+[gh-actions]
+python =
+    2.7: py27
+    3.6: py36-locale
+    3.7: py37
+    3.8: py38
+    3.9: py39
+    3.10: py310
 
 [testenv]
+changedir = {envtmpdir}
 deps =
     pytest
-commands=
-    python setup.py install
-    py.test []
+commands =
+    py.test {toxinidir}/tests {posargs}
 
-[testenv:py35-locale]
-basepython = python3.5
+[testenv:py36-locale]
+basepython = python3.6
 setenv =
     LC_ALL=C
diff --git a/update_cpp.sh b/update_cpp.sh
index 7f771a7..8f6508a 100755
--- a/update_cpp.sh
+++ b/update_cpp.sh
@@ -1,2 +1 @@
-#!/bin/sh
 cython src/*.pyx src/*.pxd -a --cplus -2