diff --git a/.gitignore b/.gitignore
--- a/.gitignore
+++ b/.gitignore
@@ -11,3 +11,4 @@
 version.txt
 /.hypothesis/
 /.tox/
+.mypy_cache/
diff --git a/MANIFEST.in b/MANIFEST.in
--- a/MANIFEST.in
+++ b/MANIFEST.in
@@ -4,3 +4,4 @@
 include requirements-swh.txt
 include version.txt
 recursive-include swh/scheduler/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-arrow.*]
+ignore_missing_imports = True
+
+[mypy-celery.*]
+ignore_missing_imports = True
+
+[mypy-elasticsearch.*]
+ignore_missing_imports = True
+
+[mypy-kombu.*]
+ignore_missing_imports = True
+
+[mypy-pkg_resources.*]
+ignore_missing_imports = True
+
+[mypy-psycopg2.*]
+ignore_missing_imports = True
+
+[mypy-pytest.*]
+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/scheduler/__init__.py b/swh/scheduler/__init__.py
--- a/swh/scheduler/__init__.py
+++ b/swh/scheduler/__init__.py
@@ -3,6 +3,8 @@
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
+from typing import Any, Dict
+
 
 # Percentage of tasks with priority to schedule
 PRIORITY_SLOT = 0.6
@@ -16,7 +18,7 @@
     })
 }
 # current configuration. To be set by the config loading mechanism
-CONFIG = {}
+CONFIG = {}  # type: Dict[str, Any]
 
 
 def compute_nb_tasks_from(num_tasks):
diff --git a/swh/scheduler/celery_backend/config.py b/swh/scheduler/celery_backend/config.py
--- a/swh/scheduler/celery_backend/config.py
+++ b/swh/scheduler/celery_backend/config.py
@@ -18,6 +18,8 @@
 
 import requests
 
+from typing import Any, Dict
+
 from swh.scheduler import CONFIG as SWH_CONFIG
 
 from swh.core.config import load_named_config, merge_configs
@@ -177,7 +179,7 @@
 
 INSTANCE_NAME = os.environ.get(CONFIG_NAME_ENVVAR)
 CONFIG_NAME = os.environ.get('SWH_CONFIG_FILENAME')
-CONFIG = {}
+CONFIG = {}  # type: Dict[str, Any]
 
 if CONFIG_NAME:
     # load the celery config from the main config file given as
@@ -186,7 +188,7 @@
     # celery specific configuration.
     SWH_CONFIG.clear()
     SWH_CONFIG.update(load_named_config(CONFIG_NAME))
-    CONFIG = SWH_CONFIG.get('celery')
+    CONFIG = SWH_CONFIG.get('celery', default={})
 
 if not CONFIG:
     # otherwise, back to compat config loading mechanism
diff --git a/swh/scheduler/py.typed b/swh/scheduler/py.typed
new file mode 100644
--- /dev/null
+++ b/swh/scheduler/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 =
@@ -28,3 +28,11 @@
   flake8
 commands =
   {envpython} -m flake8
+
+[testenv:mypy]
+skip_install = true
+deps =
+  .[testing]
+  mypy
+commands =
+  mypy swh