diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 0000000..6f7368b
--- /dev/null
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,34 @@
+name: CI
+
+on:
+  pull_request:
+  push:
+    branches: [main]
+
+jobs:
+  mypy:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v3
+    - uses: actions/setup-python@v4
+      with:
+        python-version: '3.10'
+        architecture: x64
+    - run: pip install nox==2019.11.9
+    - run: pip install poetry==1.2.2
+    - run: nox --session mypy
+
+  test:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        python-version: ['3.7', '3.8', '3.9', '3.10', '3.11']
+    steps:
+    - uses: actions/checkout@v3
+    - uses: actions/setup-python@v4
+      with:
+        python-version: ${{matrix.python-version}}
+        architecture: x64
+    - run: pip install nox==2022.11.21
+    - run: pip install poetry==1.2.2
+    - run: nox --sessions test-${{matrix.python-version}}
diff --git a/noxfile.py b/noxfile.py
index d4a832b..dd707aa 100644
--- a/noxfile.py
+++ b/noxfile.py
@@ -2,7 +2,7 @@
 
 import nox
 
-nox.options.sessions = ["clean", "test", "report", "docs"]
+nox.options.sessions = ["clean", "test", "report", "mypy"]
 nox.options.reuse_existing_virtualenvs = True
 
 
@@ -17,7 +17,7 @@ def clean(session):
 def mypy(session):
     session.install("poetry")
     session.run("poetry", "install", "--with=dev")
-    session.run("mypy", "src", "tests")
+    session.run("mypy", "pysource_minimize", "tests")
 
 
 @nox.session(python=["3.7", "3.8", "3.9", "3.10", "3.11"])
diff --git a/poetry.lock b/poetry.lock
index 29184e9..5d9b237 100644
--- a/poetry.lock
+++ b/poetry.lock
@@ -1,4 +1,4 @@
-# This file is automatically @generated by Poetry and should not be changed by hand.
+# This file is automatically @generated by Poetry 1.4.2 and should not be changed by hand.
 
 [[package]]
 name = "asttokens"
@@ -22,7 +22,7 @@ test = ["astroid (<=2.5.3)", "pytest"]
 name = "astunparse"
 version = "1.6.3"
 description = "An AST unparser for Python"
-category = "dev"
+category = "main"
 optional = false
 python-versions = "*"
 files = [
@@ -205,6 +205,66 @@ files = [
     {file = "iniconfig-1.1.1.tar.gz", hash = "sha256:bc3af051d7d14b2ee5ef9969666def0cd1a000e121eaea580d4a313df4b37f32"},
 ]
 
+[[package]]
+name = "mypy"
+version = "1.2.0"
+description = "Optional static typing for Python"
+category = "dev"
+optional = false
+python-versions = ">=3.7"
+files = [
+    {file = "mypy-1.2.0-cp310-cp310-macosx_10_9_x86_64.whl", hash = "sha256:701189408b460a2ff42b984e6bd45c3f41f0ac9f5f58b8873bbedc511900086d"},
+    {file = "mypy-1.2.0-cp310-cp310-macosx_11_0_arm64.whl", hash = "sha256:fe91be1c51c90e2afe6827601ca14353bbf3953f343c2129fa1e247d55fd95ba"},
+    {file = "mypy-1.2.0-cp310-cp310-manylinux_2_17_x86_64.manylinux2014_x86_64.whl", hash = "sha256:8d26b513225ffd3eacece727f4387bdce6469192ef029ca9dd469940158bc89e"},
+    {file = "mypy-1.2.0-cp310-cp310-musllinux_1_1_x86_64.whl", hash = "sha256:3a2d219775a120581a0ae8ca392b31f238d452729adbcb6892fa89688cb8306a"},
+    {file = "mypy-1.2.0-cp310-cp310-win_amd64.whl", hash = "sha256:2e93a8a553e0394b26c4ca683923b85a69f7ccdc0139e6acd1354cc884fe0128"},
+    {file = "mypy-1.2.0-cp311-cp311-macosx_10_9_x86_64.whl", hash = "sha256:3efde4af6f2d3ccf58ae825495dbb8d74abd6d176ee686ce2ab19bd025273f41"},
+    {file = "mypy-1.2.0-cp311-cp311-macosx_11_0_arm64.whl", hash = "sha256:695c45cea7e8abb6f088a34a6034b1d273122e5530aeebb9c09626cea6dca4cb"},
+    {file = "mypy-1.2.0-cp311-cp311-manylinux_2_17_x86_64.manylinux2014_x86_64.whl", hash = "sha256:d0e9464a0af6715852267bf29c9553e4555b61f5904a4fc538547a4d67617937"},
+    {file = "mypy-1.2.0-cp311-cp311-musllinux_1_1_x86_64.whl", hash = "sha256:8293a216e902ac12779eb7a08f2bc39ec6c878d7c6025aa59464e0c4c16f7eb9"},
+    {file = "mypy-1.2.0-cp311-cp311-win_amd64.whl", hash = "sha256:f46af8d162f3d470d8ffc997aaf7a269996d205f9d746124a179d3abe05ac602"},
+    {file = "mypy-1.2.0-cp37-cp37m-macosx_10_9_x86_64.whl", hash = "sha256:031fc69c9a7e12bcc5660b74122ed84b3f1c505e762cc4296884096c6d8ee140"},
+    {file = "mypy-1.2.0-cp37-cp37m-manylinux_2_17_x86_64.manylinux2014_x86_64.whl", hash = "sha256:390bc685ec209ada4e9d35068ac6988c60160b2b703072d2850457b62499e336"},
+    {file = "mypy-1.2.0-cp37-cp37m-musllinux_1_1_x86_64.whl", hash = "sha256:4b41412df69ec06ab141808d12e0bf2823717b1c363bd77b4c0820feaa37249e"},
+    {file = "mypy-1.2.0-cp37-cp37m-win_amd64.whl", hash = "sha256:4e4a682b3f2489d218751981639cffc4e281d548f9d517addfd5a2917ac78119"},
+    {file = "mypy-1.2.0-cp38-cp38-macosx_10_9_x86_64.whl", hash = "sha256:a197ad3a774f8e74f21e428f0de7f60ad26a8d23437b69638aac2764d1e06a6a"},
+    {file = "mypy-1.2.0-cp38-cp38-macosx_11_0_arm64.whl", hash = "sha256:c9a084bce1061e55cdc0493a2ad890375af359c766b8ac311ac8120d3a472950"},
+    {file = "mypy-1.2.0-cp38-cp38-manylinux_2_17_x86_64.manylinux2014_x86_64.whl", hash = "sha256:eaeaa0888b7f3ccb7bcd40b50497ca30923dba14f385bde4af78fac713d6d6f6"},
+    {file = "mypy-1.2.0-cp38-cp38-musllinux_1_1_x86_64.whl", hash = "sha256:bea55fc25b96c53affab852ad94bf111a3083bc1d8b0c76a61dd101d8a388cf5"},
+    {file = "mypy-1.2.0-cp38-cp38-win_amd64.whl", hash = "sha256:4c8d8c6b80aa4a1689f2a179d31d86ae1367ea4a12855cc13aa3ba24bb36b2d8"},
+    {file = "mypy-1.2.0-cp39-cp39-macosx_10_9_x86_64.whl", hash = "sha256:70894c5345bea98321a2fe84df35f43ee7bb0feec117a71420c60459fc3e1eed"},
+    {file = "mypy-1.2.0-cp39-cp39-macosx_11_0_arm64.whl", hash = "sha256:4a99fe1768925e4a139aace8f3fb66db3576ee1c30b9c0f70f744ead7e329c9f"},
+    {file = "mypy-1.2.0-cp39-cp39-manylinux_2_17_x86_64.manylinux2014_x86_64.whl", hash = "sha256:023fe9e618182ca6317ae89833ba422c411469156b690fde6a315ad10695a521"},
+    {file = "mypy-1.2.0-cp39-cp39-musllinux_1_1_x86_64.whl", hash = "sha256:4d19f1a239d59f10fdc31263d48b7937c585810288376671eaf75380b074f238"},
+    {file = "mypy-1.2.0-cp39-cp39-win_amd64.whl", hash = "sha256:2de7babe398cb7a85ac7f1fd5c42f396c215ab3eff731b4d761d68d0f6a80f48"},
+    {file = "mypy-1.2.0-py3-none-any.whl", hash = "sha256:d8e9187bfcd5ffedbe87403195e1fc340189a68463903c39e2b63307c9fa0394"},
+    {file = "mypy-1.2.0.tar.gz", hash = "sha256:f70a40410d774ae23fcb4afbbeca652905a04de7948eaf0b1789c8d1426b72d1"},
+]
+
+[package.dependencies]
+mypy-extensions = ">=1.0.0"
+tomli = {version = ">=1.1.0", markers = "python_version < \"3.11\""}
+typed-ast = {version = ">=1.4.0,<2", markers = "python_version < \"3.8\""}
+typing-extensions = ">=3.10"
+
+[package.extras]
+dmypy = ["psutil (>=4.0)"]
+install-types = ["pip"]
+python2 = ["typed-ast (>=1.4.0,<2)"]
+reports = ["lxml"]
+
+[[package]]
+name = "mypy-extensions"
+version = "1.0.0"
+description = "Type system extensions for programs checked with the mypy type checker."
+category = "dev"
+optional = false
+python-versions = ">=3.5"
+files = [
+    {file = "mypy_extensions-1.0.0-py3-none-any.whl", hash = "sha256:4392f6c0eb8a5668a69e23d168ffa70f0be9ccfd32b5cc2d26a34ae5b844552d"},
+    {file = "mypy_extensions-1.0.0.tar.gz", hash = "sha256:75dbf8955dc00442a438fc4d0666508a9a97b6bd41aa2f0ffe9d2f2725af0782"},
+]
+
 [[package]]
 name = "packaging"
 version = "21.3"
@@ -414,6 +474,40 @@ files = [
     {file = "tomli-2.0.1.tar.gz", hash = "sha256:de526c12914f0c550d15924c62d72abc48d6fe7364aa87328337a31007fe8a4f"},
 ]
 
+[[package]]
+name = "typed-ast"
+version = "1.5.4"
+description = "a fork of Python 2 and 3 ast modules with type comment support"
+category = "dev"
+optional = false
+python-versions = ">=3.6"
+files = [
+    {file = "typed_ast-1.5.4-cp310-cp310-macosx_10_9_x86_64.whl", hash = "sha256:669dd0c4167f6f2cd9f57041e03c3c2ebf9063d0757dc89f79ba1daa2bfca9d4"},
+    {file = "typed_ast-1.5.4-cp310-cp310-macosx_11_0_arm64.whl", hash = "sha256:211260621ab1cd7324e0798d6be953d00b74e0428382991adfddb352252f1d62"},
+    {file = "typed_ast-1.5.4-cp310-cp310-manylinux_2_17_aarch64.manylinux2014_aarch64.whl", hash = "sha256:267e3f78697a6c00c689c03db4876dd1efdfea2f251a5ad6555e82a26847b4ac"},
+    {file = "typed_ast-1.5.4-cp310-cp310-manylinux_2_5_x86_64.manylinux1_x86_64.manylinux_2_12_x86_64.manylinux2010_x86_64.whl", hash = "sha256:c542eeda69212fa10a7ada75e668876fdec5f856cd3d06829e6aa64ad17c8dfe"},
+    {file = "typed_ast-1.5.4-cp310-cp310-win_amd64.whl", hash = "sha256:a9916d2bb8865f973824fb47436fa45e1ebf2efd920f2b9f99342cb7fab93f72"},
+    {file = "typed_ast-1.5.4-cp36-cp36m-macosx_10_9_x86_64.whl", hash = "sha256:79b1e0869db7c830ba6a981d58711c88b6677506e648496b1f64ac7d15633aec"},
+    {file = "typed_ast-1.5.4-cp36-cp36m-manylinux_2_17_aarch64.manylinux2014_aarch64.whl", hash = "sha256:a94d55d142c9265f4ea46fab70977a1944ecae359ae867397757d836ea5a3f47"},
+    {file = "typed_ast-1.5.4-cp36-cp36m-manylinux_2_5_x86_64.manylinux1_x86_64.manylinux_2_12_x86_64.manylinux2010_x86_64.whl", hash = "sha256:183afdf0ec5b1b211724dfef3d2cad2d767cbefac291f24d69b00546c1837fb6"},
+    {file = "typed_ast-1.5.4-cp36-cp36m-win_amd64.whl", hash = "sha256:639c5f0b21776605dd6c9dbe592d5228f021404dafd377e2b7ac046b0349b1a1"},
+    {file = "typed_ast-1.5.4-cp37-cp37m-macosx_10_9_x86_64.whl", hash = "sha256:cf4afcfac006ece570e32d6fa90ab74a17245b83dfd6655a6f68568098345ff6"},
+    {file = "typed_ast-1.5.4-cp37-cp37m-manylinux_2_17_aarch64.manylinux2014_aarch64.whl", hash = "sha256:ed855bbe3eb3715fca349c80174cfcfd699c2f9de574d40527b8429acae23a66"},
+    {file = "typed_ast-1.5.4-cp37-cp37m-manylinux_2_5_x86_64.manylinux1_x86_64.manylinux_2_12_x86_64.manylinux2010_x86_64.whl", hash = "sha256:6778e1b2f81dfc7bc58e4b259363b83d2e509a65198e85d5700dfae4c6c8ff1c"},
+    {file = "typed_ast-1.5.4-cp37-cp37m-win_amd64.whl", hash = "sha256:0261195c2062caf107831e92a76764c81227dae162c4f75192c0d489faf751a2"},
+    {file = "typed_ast-1.5.4-cp38-cp38-macosx_10_9_x86_64.whl", hash = "sha256:2efae9db7a8c05ad5547d522e7dbe62c83d838d3906a3716d1478b6c1d61388d"},
+    {file = "typed_ast-1.5.4-cp38-cp38-macosx_11_0_arm64.whl", hash = "sha256:7d5d014b7daa8b0bf2eaef684295acae12b036d79f54178b92a2b6a56f92278f"},
+    {file = "typed_ast-1.5.4-cp38-cp38-manylinux_2_17_aarch64.manylinux2014_aarch64.whl", hash = "sha256:370788a63915e82fd6f212865a596a0fefcbb7d408bbbb13dea723d971ed8bdc"},
+    {file = "typed_ast-1.5.4-cp38-cp38-manylinux_2_5_x86_64.manylinux1_x86_64.manylinux_2_12_x86_64.manylinux2010_x86_64.whl", hash = "sha256:4e964b4ff86550a7a7d56345c7864b18f403f5bd7380edf44a3c1fb4ee7ac6c6"},
+    {file = "typed_ast-1.5.4-cp38-cp38-win_amd64.whl", hash = "sha256:683407d92dc953c8a7347119596f0b0e6c55eb98ebebd9b23437501b28dcbb8e"},
+    {file = "typed_ast-1.5.4-cp39-cp39-macosx_10_9_x86_64.whl", hash = "sha256:4879da6c9b73443f97e731b617184a596ac1235fe91f98d279a7af36c796da35"},
+    {file = "typed_ast-1.5.4-cp39-cp39-macosx_11_0_arm64.whl", hash = "sha256:3e123d878ba170397916557d31c8f589951e353cc95fb7f24f6bb69adc1a8a97"},
+    {file = "typed_ast-1.5.4-cp39-cp39-manylinux_2_17_aarch64.manylinux2014_aarch64.whl", hash = "sha256:ebd9d7f80ccf7a82ac5f88c521115cc55d84e35bf8b446fcd7836eb6b98929a3"},
+    {file = "typed_ast-1.5.4-cp39-cp39-manylinux_2_5_x86_64.manylinux1_x86_64.manylinux_2_12_x86_64.manylinux2010_x86_64.whl", hash = "sha256:98f80dee3c03455e92796b58b98ff6ca0b2a6f652120c263efdba4d6c5e58f72"},
+    {file = "typed_ast-1.5.4-cp39-cp39-win_amd64.whl", hash = "sha256:0fdbcf2fef0ca421a3f5912555804296f0b0960f0418c440f5d6d3abb549f3e1"},
+    {file = "typed_ast-1.5.4.tar.gz", hash = "sha256:39e21ceb7388e4bb37f4c679d72707ed46c2fbf2a5609b8b8ebc4b067d977df2"},
+]
+
 [[package]]
 name = "typing-extensions"
 version = "4.4.0"
@@ -430,7 +524,7 @@ files = [
 name = "wheel"
 version = "0.38.4"
 description = "A built-package format for Python"
-category = "dev"
+category = "main"
 optional = false
 python-versions = ">=3.7"
 files = [
@@ -460,4 +554,4 @@ testing = ["flake8 (<5)", "func-timeout", "jaraco.functools", "jaraco.itertools"
 [metadata]
 lock-version = "2.0"
 python-versions = "^3.7"
-content-hash = "6160a488123d610f3c131efa3bba4642badd5e72485d4ee8af5493a8d8643a36"
+content-hash = "67b8ccc412caea8b92ceec60510049dc894494eefb071adae9949375bc36ecd6"
diff --git a/pyproject.toml b/pyproject.toml
index 1fae718..83218d7 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -19,6 +19,7 @@ pytest-subtests = "^0.8.0"
 pytest-xdist = {extras = ["psutil"], version = "^3.1.0"}
 coverage-enable-subprocess = "^1.0"
 coverage = "^6.5.0"
+mypy = "^1.2.0"
 
 [build-system]
 requires = ["poetry-core"]
diff --git a/pysource_minimize/_minimize.py b/pysource_minimize/_minimize.py
index e0c23dd..f8d5771 100644
--- a/pysource_minimize/_minimize.py
+++ b/pysource_minimize/_minimize.py
@@ -9,7 +9,7 @@
     from ast import unparse
 except ImportError:
 
-    from astunparse import unparse
+    from astunparse import unparse  # type: ignore
 
 TESTING = "PYTEST_CURRENT_TEST" in os.environ