diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 3343606..d267021 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -40,3 +40,21 @@ repos:
         files: "^tests/"
         args:
           - --disable=missing-docstring,consider-using-f-string,duplicate-code
+  - repo: local
+  # We do not use pre-commit/mirrors-mypy,
+  # as it comes with opinionated defaults
+  # (like --ignore-missing-imports)
+  # and is difficult to configure to run
+  # with the dependencies correctly installed.
+    hooks:
+    - id: mypy
+      name: mypy
+      entry: "python3 etc/run_mypy.py"
+      language: python
+      additional_dependencies: ["mypy==0.790", "tomlkit"]
+      types: [python]
+      # use require_serial so that script
+      # is only called once per commit
+      require_serial: true
+      # Print the number of files as a sanity-check
+      verbose: true
diff --git a/adafruit_pioasm.py b/adafruit_pioasm.py
index a6a4ebf..9c1a433 100644
--- a/adafruit_pioasm.py
+++ b/adafruit_pioasm.py
@@ -14,6 +14,11 @@
 import array
 import re
 
+try:
+    from typing import List, Tuple, Optional
+except:  # pylint: disable=bare-except
+    pass
+
 splitter = re.compile(r",\s*|\s+(?:,\s*)?").split
 mov_splitter = re.compile("!|~|::").split
 
@@ -40,14 +45,16 @@ class Program:  # pylint: disable=too-few-public-methods
 
     """
 
-    def __init__(self, text_program: str, *, build_debuginfo=False) -> None:
+    debuginfo: Optional[Tuple[List[int], str]]
+
+    def __init__(self, text_program: str, *, build_debuginfo: bool = False) -> None:
         """Converts pioasm text to encoded instruction bytes"""
         # pylint: disable=too-many-branches,too-many-statements,too-many-locals
-        assembled = []
+        assembled: List[int] = []
         program_name = None
         labels = {}
         linemap = []
-        instructions = []
+        instructions: List[str] = []
         sideset_count = 0
         sideset_enable = 0
         wrap = None
@@ -83,9 +90,9 @@ def __init__(self, text_program: str, *, build_debuginfo=False) -> None:
 
         max_delay = 2 ** (5 - sideset_count - sideset_enable) - 1
         assembled = []
-        for instruction in instructions:
+        for instruction_str in instructions:
             # print(instruction)
-            instruction = splitter(instruction.strip())
+            instruction = splitter(instruction_str.strip())
             delay = 0
             if instruction[-1].endswith("]"):  # Delay
                 delay = int(instruction[-1].strip("[]"), 0)
@@ -242,14 +249,14 @@ def __init__(self, text_program: str, *, build_debuginfo=False) -> None:
         else:
             self.debuginfo = None
 
-    def print_c_program(self, name, qualifier="const"):
+    def print_c_program(self, name: str, qualifier: str = "const") -> None:
         """Print the program into a C program snippet"""
-        if self.debuginfo is None:
-            linemap = None
-            program_lines = None
-        else:
+        if self.debuginfo:
             linemap = self.debuginfo[0][:]  # Use a copy since we destroy it
             program_lines = self.debuginfo[1].split("\n")
+        else:
+            linemap = []
+            program_lines = []
 
         print(
             f"{qualifier} int {name}_wrap = {self.pio_kwargs.get('wrap', len(self.assembled)-1)};"
@@ -290,7 +297,7 @@ def print_c_program(self, name, qualifier="const"):
         print()
 
 
-def assemble(program_text: str) -> array.array:
+def assemble(program_text: str) -> "array.array[int]":
     """Converts pioasm text to encoded instruction bytes
 
     In new code, prefer to use the `Program` class so that the extra arguments
diff --git a/etc/run_mypy.py b/etc/run_mypy.py
new file mode 100755
index 0000000..f7a9c83
--- /dev/null
+++ b/etc/run_mypy.py
@@ -0,0 +1,33 @@
+#!/usr/bin/python3
+# SPDX-FileCopyrightText: 2022 Jeff Epler, written for Adafruit Industries
+#
+# SPDX-License-Identifier: Unlicense
+"""Automatically run mypy. Use from pre-commit"""
+import os
+import pathlib
+import subprocess
+import tomlkit
+
+
+def print_check_call(command):
+    """Keep the user aware of commands being executed"""
+    print("# Running", " ".join(command))
+    subprocess.check_call(command)
+
+
+os.chdir(pathlib.Path(__file__).parent.parent)
+
+pip_command = ["pip", "install", "--no-input", "--quiet", "--editable", "."]
+print_check_call(pip_command)
+
+with open("pyproject.toml") as f:
+    meta = tomlkit.load(f)
+mypy_command = ["mypy"]
+if meta["tool"].get("adafruit", {}).get("mypy-strict", True):
+    mypy_command.append("--strict")
+for module in meta["tool"]["setuptools"].get("py-modules", []):
+    mypy_command.extend(["-m", module])
+for module in meta["tool"]["setuptools"].get("packages", []):
+    mypy_command.extend(["-p", module])
+
+print_check_call(mypy_command)