diff --git a/.github/workflows/tox.yml b/.github/workflows/tox.yml
index e0e95e66..e6edf851 100644
--- a/.github/workflows/tox.yml
+++ b/.github/workflows/tox.yml
@@ -44,3 +44,5 @@ jobs:
         pip install tox tox-gh-actions
     - name: Linter
       run: tox -e py37-invalidcode
+    - name: Mypy
+      run: tox -e py37-mypy
diff --git a/moulinette/actionsmap.py b/moulinette/actionsmap.py
index b465f33d..386018ec 100644
--- a/moulinette/actionsmap.py
+++ b/moulinette/actionsmap.py
@@ -6,6 +6,7 @@ import logging
 import glob
 import pickle as pickle
 
+from typing import List, Optional
 from time import time
 from collections import OrderedDict
 from importlib import import_module
@@ -30,7 +31,6 @@ logger = logging.getLogger("moulinette.actionsmap")
 
 
 class _ExtraParameter(object):
-
     """
     Argument parser for an extra parameter.
 
@@ -39,21 +39,14 @@ class _ExtraParameter(object):
 
     """
 
+    name: Optional[str] = None
+
+    """A list of interface for which the parameter doesn't apply to"""
+    skipped_iface: List[str] = []
+
     def __init__(self, iface):
         self.iface = iface
 
-    # Required variables
-    # Each extra parameters classes must overwrite these variables.
-
-    """The extra parameter name"""
-    name = None
-
-    # Optional variables
-    # Each extra parameters classes can overwrite these variables.
-
-    """A list of interface for which the parameter doesn't apply"""
-    skipped_iface = []
-
     # Virtual methods
     # Each extra parameters classes can implement these methods.
 
@@ -621,7 +614,7 @@ class ActionsMap(object):
 
         # This var is ['*'] by default but could be set for example to
         # ['yunohost', 'yml_*']
-        NAMESPACE_PATTERNS = env["NAMESPACES"]
+        NAMESPACE_PATTERNS = env["NAMESPACES"].split()
 
         # Look for all files that match the given patterns in the actionsmap dir
         for namespace_pattern in NAMESPACE_PATTERNS:
diff --git a/moulinette/core.py b/moulinette/core.py
index 3aa024ec..4c0bdcf8 100644
--- a/moulinette/core.py
+++ b/moulinette/core.py
@@ -22,8 +22,6 @@ for key in env.keys():
     if value_from_environ:
         env[key] = value_from_environ
 
-env["NAMESPACES"] = env["NAMESPACES"].split()
-
 
 def during_unittests_run():
     return "TESTS_RUN" in os.environ
diff --git a/moulinette/interfaces/__init__.py b/moulinette/interfaces/__init__.py
index a5d32cac..d8bed853 100644
--- a/moulinette/interfaces/__init__.py
+++ b/moulinette/interfaces/__init__.py
@@ -7,6 +7,7 @@ import copy
 import datetime
 from collections import deque, OrderedDict
 from json.encoder import JSONEncoder
+from typing import Optional
 
 from moulinette import m18n
 from moulinette.core import MoulinetteError
@@ -44,7 +45,7 @@ class BaseActionsMapParser(object):
     # Each parser classes must implement these properties.
 
     """The name of the interface for which it is the parser"""
-    interface = None
+    interface: Optional[str] = None
 
     # Virtual methods
     # Each parser classes must implement these methods.
diff --git a/moulinette/interfaces/api.py b/moulinette/interfaces/api.py
index 2b57c3c4..9350c76e 100644
--- a/moulinette/interfaces/api.py
+++ b/moulinette/interfaces/api.py
@@ -268,6 +268,7 @@ class Session:
 
         return infos
 
+    @staticmethod
     def delete_infos():
 
         response.set_cookie(f"session.{Session.actionsmap_name}", "", max_age=-1)
diff --git a/tox.ini b/tox.ini
index 3ffa1342..7fa1cf6a 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,6 +1,6 @@
 [tox]
 envlist =
-  py37-{pytest,lint,invalidcode}
+  py37-{pytest,lint,invalidcode,mypy}
   format
   format-check
   docs
@@ -14,10 +14,12 @@ deps =
   py37-pytest: .[tests]
   py37-lint: flake8
   py37-invalidcode: flake8
+  py37-mypy: mypy >= 0.761
 commands =
     py37-pytest: pytest {posargs} -c pytest.ini
     py37-lint: flake8 moulinette test
     py37-invalidcode: flake8 moulinette test --select F
+    py37-mypy: mypy  --ignore-missing-imports --install-types --non-interactive moulinette/
 
 [gh-actions]
 python =