diff --git a/.gitignore b/.gitignore
--- a/.gitignore
+++ b/.gitignore
@@ -10,3 +10,4 @@
 *.egg-info
 version.txt
 .tox/
+.mypy_cache/
diff --git a/MANIFEST.in b/MANIFEST.in
--- a/MANIFEST.in
+++ b/MANIFEST.in
@@ -7,3 +7,4 @@
 include version.txt
 recursive-include sql *.sql
 recursive-include swh/vault/sql *.sql
+recursive-include swh py.typed
diff --git a/mypy.ini b/mypy.ini
new file mode 100644
--- /dev/null
+++ b/mypy.ini
@@ -0,0 +1,27 @@
+[mypy]
+namespace_packages = True
+warn_unused_ignores = True
+
+
+# 3rd party libraries without stubs (yet)
+
+[mypy-celery.*]
+ignore_missing_imports = True
+
+[mypy-dulwich.*]
+ignore_missing_imports = True
+
+[mypy-fastimport.*]
+ignore_missing_imports = True
+
+[mypy-pkg_resources.*]
+ignore_missing_imports = True
+
+[mypy-psycopg2.*]
+ignore_missing_imports = True
+
+[mypy-pytest.*]
+ignore_missing_imports = True
+
+[mypy-pytest_postgresql.*]
+ignore_missing_imports = True
diff --git a/requirements-test.txt b/requirements-test.txt
--- a/requirements-test.txt
+++ b/requirements-test.txt
@@ -1,5 +1,5 @@
 pytest < 4
 pytest-postgresql
 dulwich >= 0.18.7
-swh.loader.git >= 0.0.48
+swh.loader.git >= 0.0.52
 swh.storage[testing]
diff --git a/swh/__init__.py b/swh/__init__.py
--- a/swh/__init__.py
+++ b/swh/__init__.py
@@ -1 +1,4 @@
-__path__ = __import__('pkgutil').extend_path(__path__, __name__)
+from pkgutil import extend_path
+from typing import Iterable
+
+__path__ = extend_path(__path__, __name__)  # type: Iterable[str]
diff --git a/swh/vault/cookers/base.py b/swh/vault/cookers/base.py
--- a/swh/vault/cookers/base.py
+++ b/swh/vault/cookers/base.py
@@ -6,7 +6,9 @@
 import abc
 import io
 import logging
+
 from psycopg2.extensions import QueryCanceledError
+from typing import Optional
 
 from swh.model import hashutil
 
@@ -62,7 +64,7 @@
     - CACHE_TYPE_KEY: key to use for the bundle to reference in cache
     - def cook(): cook the object into a bundle
     """
-    CACHE_TYPE_KEY = None
+    CACHE_TYPE_KEY = None  # type: Optional[str]
 
     def __init__(self, obj_type, obj_id, backend, storage,
                  max_bundle_size=MAX_BUNDLE_SIZE):
diff --git a/swh/vault/py.typed b/swh/vault/py.typed
new file mode 100644
--- /dev/null
+++ b/swh/vault/py.typed
@@ -0,0 +1 @@
+# Marker file for PEP 561.
diff --git a/tox.ini b/tox.ini
--- a/tox.ini
+++ b/tox.ini
@@ -1,5 +1,5 @@
 [tox]
-envlist=flake8,py3
+envlist=flake8,mypy,py3
 
 [testenv:py3]
 deps =
@@ -16,3 +16,11 @@
   flake8
 commands =
   {envpython} -m flake8
+
+[testenv:mypy]
+skip_install = true
+deps =
+  .[testing]
+  mypy
+commands =
+  mypy swh