diff --git a/library/ceph_config.py b/library/ceph_config.py
index 57df331..d7a52b7 100644
--- a/library/ceph_config.py
+++ b/library/ceph_config.py
@@ -3,7 +3,7 @@
 # Author: Guillaume Abrioux <gabrioux@redhat.com>
 
 from __future__ import absolute_import, division, print_function
-from typing import List, Tuple
+from typing import Any, Dict, List, Tuple, Union
 __metaclass__ = type
 
 from ansible.module_utils.basic import AnsibleModule  # type: ignore
@@ -97,7 +97,7 @@ def set_option(module: "AnsibleModule",
     return rc, cmd, out.strip(), err
 
 
-def get_config_dump(module: "AnsibleModule"):
+def get_config_dump(module: "AnsibleModule") -> Tuple[int, List[str], str, str]:
     cmd = build_base_cmd_shell(module)
     cmd.extend(['ceph', 'config', 'dump', '--format', 'json'])
     rc, out, err = module.run_command(cmd)
@@ -107,7 +107,7 @@ def get_config_dump(module: "AnsibleModule"):
     return rc, cmd, out, err
 
 
-def get_current_value(who, option, config_dump):
+def get_current_value(who: str, option: str, config_dump: List[Dict[str, Any]]) -> Union[str, None]:
     for config in config_dump:
         if config['section'] == who and config['name'] == option:
             return config['value']
diff --git a/library/ceph_orch_apply.py b/library/ceph_orch_apply.py
index a397328..f110618 100644
--- a/library/ceph_orch_apply.py
+++ b/library/ceph_orch_apply.py
@@ -82,7 +82,7 @@ def apply_spec(module: "AnsibleModule",
     return rc, cmd, out, err
 
 
-def main():
+def main() -> None:
     module = AnsibleModule(
         argument_spec=dict(
             fsid=dict(type='str', required=False),
diff --git a/library/cephadm_bootstrap.py b/library/cephadm_bootstrap.py
index 7f34c8d..15ae6e4 100644
--- a/library/cephadm_bootstrap.py
+++ b/library/cephadm_bootstrap.py
@@ -249,14 +249,14 @@ def run_module() -> None:
     ceph_pubkey = 'ceph.pub'
 
     def extend_append(key: str, parameters: dict) -> None:
-        if parameters[key]["type"] == 'bool':
-            cmd.append("--" + k.replace('_', '-'))
+        if parameters[key]['type'] == 'bool':
+            cmd.append('--' + k.replace('_', '-'))
         else:
-            cmd.extend(["--" + k.replace('_', '-'), module.params.get(k)])
+            cmd.extend(['--' + k.replace('_', '-'), module.params.get(k)])
 
     if fsid:
         if os.path.exists(os.path.join(data_dir, fsid)):
-            out = f"A cluster with fsid {fsid} is already deployed."
+            out = f'A cluster with fsid {fsid} is already deployed.'
             exit_module(
                 rc=0,
                 startd=startd,
@@ -270,8 +270,9 @@ def extend_append(key: str, parameters: dict) -> None:
               ceph_keyring,
               ceph_pubkey]:
         if not allow_overwrite:
-            if os.path.exists(os.path.join(data_dir, f)):
-                out = '{} already exists, skipping.'
+            path: str = os.path.join(data_dir, f)
+            if os.path.exists(path):
+                out = f'{path} already exists, skipping.'
                 exit_module(
                     rc=0,
                     startd=startd,
@@ -339,7 +340,7 @@ def extend_append(key: str, parameters: dict) -> None:
         )
 
 
-def main():
+def main() -> None:
     run_module()
 
 
diff --git a/module_utils/ceph_common.py b/module_utils/ceph_common.py
index 99c5da8..cc19df4 100644
--- a/module_utils/ceph_common.py
+++ b/module_utils/ceph_common.py
@@ -1,14 +1,16 @@
 import datetime
 import time
-from typing import TYPE_CHECKING, List, Dict
+from typing import TYPE_CHECKING, Any, List, Dict, Callable, Type, TypeVar
 
 if TYPE_CHECKING:
     from ansible.module_utils.basic import AnsibleModule  # type: ignore
 
+ExceptionType = TypeVar('ExceptionType', bound=BaseException)
 
-def retry(exceptions, retries=20, delay=1):
-    def decorator(f):
-        def _retry(*args, **kwargs):
+
+def retry(exceptions: Type[ExceptionType], retries: int = 20, delay: int = 1) -> Callable:
+    def decorator(f: Callable) -> Callable:
+        def _retry(*args: Any, **kwargs: Any) -> Callable:
             _tries = retries
             while _tries > 1:
                 try:
diff --git a/mypy.ini b/mypy.ini
new file mode 100644
index 0000000..fd210cd
--- /dev/null
+++ b/mypy.ini
@@ -0,0 +1,9 @@
+[mypy]
+strict_optional = True
+no_implicit_optional = True
+warn_incomplete_stub = True
+check_untyped_defs = True
+show_error_context = True
+allow_redefinition = True
+disallow_untyped_defs = True
+
diff --git a/tox.ini b/tox.ini
index 35fad01..f5aa3f0 100644
--- a/tox.ini
+++ b/tox.ini
@@ -8,7 +8,7 @@ skipsdist = True
 basepython = python3
 deps =
     mypy
-commands = mypy {toxinidir}/library {toxinidir}/module_utils
+commands = mypy --config-file ./mypy.ini {toxinidir}/library {toxinidir}/module_utils
 
 [testenv:flake8]
 basepython = python3