diff --git a/.gitignore b/.gitignore
--- a/.gitignore
+++ b/.gitignore
@@ -15,3 +15,4 @@
 kafka*.tar.gz*
 swh/journal/tests/kafka*
 .hypothesis/
+.mypy_cache/
diff --git a/MANIFEST.in b/MANIFEST.in
--- a/MANIFEST.in
+++ b/MANIFEST.in
@@ -2,3 +2,4 @@
 include requirements.txt
 include requirements-swh.txt
 include version.txt
+recursive-include swh py.typed
diff --git a/mypy.ini b/mypy.ini
new file mode 100644
--- /dev/null
+++ b/mypy.ini
@@ -0,0 +1,21 @@
+[mypy]
+namespace_packages = True
+warn_unused_ignores = True
+
+
+# 3rd party libraries without stubs (yet)
+
+[mypy-confluent_kafka.*]
+ignore_missing_imports = True
+
+[mypy-msgpack.*]
+ignore_missing_imports = True
+
+[mypy-pkg_resources.*]
+ignore_missing_imports = True
+
+[mypy-pytest.*]
+ignore_missing_imports = True
+
+[mypy-pytest_kafka.*]
+ignore_missing_imports = True
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/journal/py.typed b/swh/journal/py.typed
new file mode 100644
--- /dev/null
+++ b/swh/journal/py.typed
@@ -0,0 +1 @@
+# Marker file for PEP 561.
diff --git a/swh/journal/tests/conftest.py b/swh/journal/tests/conftest.py
--- a/swh/journal/tests/conftest.py
+++ b/swh/journal/tests/conftest.py
@@ -11,7 +11,7 @@
 
 from confluent_kafka import Consumer
 from subprocess import Popen
-from typing import Tuple, Dict
+from typing import Any, Dict, List, Optional, Tuple
 
 from pathlib import Path
 from pytest_kafka import (
@@ -154,7 +154,7 @@
     'release': ('id', RELEASES),
     'origin': (None, ORIGINS),
     'origin_visit': (None, ORIGIN_VISITS),
-}
+}  # type: Dict[str, Tuple[Optional[str], List[Dict[str, Any]]]]
 
 
 KAFKA_ROOT = os.environ.get('SWH_KAFKA_ROOT')
diff --git a/swh/journal/tests/test_cli.py b/swh/journal/tests/test_cli.py
--- a/swh/journal/tests/test_cli.py
+++ b/swh/journal/tests/test_cli.py
@@ -8,7 +8,7 @@
 import re
 import tempfile
 from subprocess import Popen
-from typing import Tuple
+from typing import Any, Dict, Tuple
 from unittest.mock import patch
 
 from click.testing import CliRunner
@@ -81,7 +81,7 @@
             'target_type': 'revision',
             'target': b'\x01'*20,
         }
-    }}
+    }}  # type: Dict[str, Any]
     producer.produce(
         topic=kafka_prefix+'.snapshot',
         key=key_to_kafka(snapshot['id']),
diff --git a/tox.ini b/tox.ini
--- a/tox.ini
+++ b/tox.ini
@@ -1,5 +1,5 @@
 [tox]
-envlist=flake8,py3-no-origin-ids,py3
+envlist=flake8,mypy,py3-no-origin-ids,py3
 
 [testenv:py3]
 passenv=SWH_KAFKA_ROOT
@@ -25,3 +25,11 @@
   flake8
 commands =
   {envpython} -m flake8
+
+[testenv:mypy]
+skip_install = true
+deps =
+  .[testing]
+  mypy
+commands =
+  mypy swh