diff --git a/.gitignore b/.gitignore
index 76c77c6..f00bf05 100644
--- a/.gitignore
+++ b/.gitignore
@@ -4,3 +4,4 @@ __pycache__/
 /setup.py
 *.egg-info
 /dist/
+.mypy_cache/
diff --git a/.travis.yml b/.travis.yml
index 4a2f296..62313e0 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -42,3 +42,6 @@ matrix:
 
     - python: "3.7"
       env: ENV=flake8
+
+    - python: "3.7"
+      env: ENV=typing
diff --git a/dephell_setuptools/_base.py b/dephell_setuptools/_base.py
index 51f9054..99fa3f4 100644
--- a/dephell_setuptools/_base.py
+++ b/dephell_setuptools/_base.py
@@ -1,8 +1,9 @@
 # built-in
 from pathlib import Path
-from typing import Union
+from typing import Any, Dict, Union
 
 # app
+from ._cached_property import cached_property
 from ._constants import FIELDS
 
 
@@ -21,7 +22,7 @@ def _normalize_path(path: Union[str, Path], default_name: str) -> Path:
         return path
 
     @staticmethod
-    def _clean(data: dict):
+    def _clean(data: Dict[str, Any]) -> Dict[str, Any]:
         result = dict()
         for k, v in data.items():
             if k not in FIELDS:
@@ -37,3 +38,7 @@ def _clean(data: dict):
             result['keywords'] = sum((kw.split() for kw in result['keywords']), [])
 
         return result
+
+    @cached_property
+    def content(self) -> Dict[str, Any]:
+        raise NotImplementedError
diff --git a/dephell_setuptools/_cfg.py b/dephell_setuptools/_cfg.py
index 9788a5c..29b5b9e 100644
--- a/dephell_setuptools/_cfg.py
+++ b/dephell_setuptools/_cfg.py
@@ -2,13 +2,14 @@
 from configparser import ConfigParser
 from copy import deepcopy
 from pathlib import Path
-from typing import Dict, List, Optional, Union
+from typing import Any, Dict, Union
 
 # external
 from setuptools.config import ConfigMetadataHandler, ConfigOptionsHandler
 
 # app
 from ._base import BaseReader
+from ._cached_property import cached_property
 from ._constants import FIELDS
 
 
@@ -16,8 +17,8 @@ class CfgReader(BaseReader):
     def __init__(self, path: Union[str, Path]):
         self.path = self._normalize_path(path, default_name='setup.cfg')
 
-    @property
-    def content(self) -> Optional[Dict[str, Union[List, Dict]]]:
+    @cached_property
+    def content(self) -> Dict[str, Any]:
         path = self.path
         if path.name == 'setup.py':
             path = path.parent / 'setup.cfg'
@@ -27,7 +28,7 @@ def content(self) -> Optional[Dict[str, Union[List, Dict]]]:
         parser = ConfigParser()
         parser.read(str(path))
 
-        options = deepcopy(parser._sections)
+        options = deepcopy(parser._sections)  # type: ignore
         for section, content in options.items():
             for k, v in content.items():
                 options[section][k] = ('', v)
diff --git a/dephell_setuptools/_cmd.py b/dephell_setuptools/_cmd.py
index a9bcc75..ab14980 100644
--- a/dephell_setuptools/_cmd.py
+++ b/dephell_setuptools/_cmd.py
@@ -7,9 +7,11 @@
 from distutils.core import Command
 from pathlib import Path
 from tempfile import NamedTemporaryFile
+from typing import Any, Dict
 
 # app
 from ._base import BaseReader
+from ._cached_property import cached_property
 from ._constants import FIELDS
 
 
@@ -24,8 +26,8 @@ def cd(path: Path):
 
 
 class CommandReader(BaseReader):
-    @property
-    def content(self):
+    @cached_property
+    def content(self) -> Dict[str, Any]:
         # generate a temporary json file which contains the metadata
         output_json = NamedTemporaryFile()
         cmd = [
@@ -44,11 +46,11 @@ def content(self):
                 env={'PYTHONPATH': str(Path(__file__).parent.parent)},
             )
         if result.returncode != 0:
-            return None
+            raise RuntimeError(result.stderr.decode().split('\n')[-1])
 
         with open(output_json.name) as stream:
-            result = json.load(stream)
-        return self._clean(result)
+            content = json.load(stream)
+        return self._clean(content)
 
 
 class JSONCommand(Command):
diff --git a/dephell_setuptools/_manager.py b/dephell_setuptools/_manager.py
index 8ccdaa4..0833e6a 100644
--- a/dephell_setuptools/_manager.py
+++ b/dephell_setuptools/_manager.py
@@ -1,9 +1,10 @@
 # built-in
 from logging import getLogger
 from pathlib import Path
-from typing import Any, Callable, Iterable, Union
+from typing import Any, Callable, Dict, Iterable, Union, Type
 
 # app
+from ._base import BaseReader
 from ._cfg import CfgReader
 from ._cmd import CommandReader
 from ._pkginfo import PkgInfoReader
@@ -22,8 +23,8 @@
 def read_setup(*,
                path: Union[str, Path],
                error_handler: Callable[[Exception], Any] = logger.exception,
-               readers: Iterable = ALL_READERS):
-    result = dict()
+               readers: Iterable[Type[BaseReader]] = ALL_READERS) -> Dict[str, Any]:
+    result = dict()     # type: Dict[str, Any]
     for reader in readers:
         try:
             content = reader(path=path).content
diff --git a/dephell_setuptools/_pkginfo.py b/dephell_setuptools/_pkginfo.py
index 3b35ae6..49a7574 100644
--- a/dephell_setuptools/_pkginfo.py
+++ b/dephell_setuptools/_pkginfo.py
@@ -1,20 +1,22 @@
 # built-in
 import json
 import subprocess
+from typing import Any, Dict
 
 # app
 from ._base import BaseReader
+from ._cached_property import cached_property
 
 
 class PkgInfoReader(BaseReader):
-    @property
-    def content(self):
+    @cached_property
+    def content(self) -> Dict[str, Any]:
         if self.path.is_file() and self.path.name != 'setup.py':
-            return None
+            raise NameError('cannot parse non setup.py named files')
 
         cmd = ['pkginfo', '--json', str(self.path)]
         result = subprocess.run(cmd, stderr=subprocess.PIPE, stdout=subprocess.PIPE)
         if result.returncode != 0:
-            return None
+            raise RuntimeError(result.stderr.decode().split('\n')[-1])
         content = json.loads(result.stdout.decode())
         return self._clean(content)
diff --git a/dephell_setuptools/_static.py b/dephell_setuptools/_static.py
index 19fc592..01e3801 100644
--- a/dephell_setuptools/_static.py
+++ b/dephell_setuptools/_static.py
@@ -1,6 +1,6 @@
 # built-in
 import ast
-from typing import Any, Dict, List, Optional, Union
+from typing import Any, Dict, Optional
 
 # app
 from ._base import BaseReader
@@ -9,9 +9,9 @@
 
 class StaticReader(BaseReader):
     @cached_property
-    def content(self) -> Optional[Dict[str, Union[List, Dict]]]:
+    def content(self) -> Dict[str, Any]:
         if not self.call:
-            return None
+            raise LookupError('cannot find setup()')
         result = self._get_call_kwargs(self.call)
         return self._clean(result)
 
diff --git a/pyproject.toml b/pyproject.toml
index 009eca8..3515aa6 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -13,7 +13,11 @@ from = {format = "pip", path = "requirements-flake.txt"}
 python = ">=3.6"
 command = "flake8"
 
-# -- FLIT -- #
+[tool.dephell.typing]
+from = {format = "flit", path = "pyproject.toml"}
+envs = ["main", "dev"]
+command = "mypy --ignore-missing-imports --allow-redefinition dephell_setuptools"
+
 
 [tool.flit.metadata]
 module="dephell_setuptools"
@@ -40,6 +44,7 @@ classifiers=[
 
 [tool.flit.metadata.requires-extra]
 dev = [
+    "mypy",
     "pkginfo",
     "pytest",
 ]