diff --git a/.travis.yml b/.travis.yml
index 9b05705..a060130 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -19,6 +19,7 @@ script:
   - pycodestyle --max-line-length=119 $(find ipython2cwl -name '*.py')
   - coverage run --source ipython2cwl -m unittest discover tests
   - coveralls
+  - make mypy
 matrix:
   include:
     - name: "Python 3.7 on macOS 10.13"
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..b920674
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,2 @@
+mypy:
+	 mypy $$(find ipython2cwl -name '*.py')
diff --git a/ipython2cwl/cwltoolextractor.py b/ipython2cwl/cwltoolextractor.py
index 61ac743..573ac94 100644
--- a/ipython2cwl/cwltoolextractor.py
+++ b/ipython2cwl/cwltoolextractor.py
@@ -7,12 +7,12 @@
 from collections import namedtuple
 from copy import deepcopy
 from pathlib import Path
-from typing import Dict, Any, List
+from typing import Dict, Any, List, Tuple
 
-import astor
-import nbconvert
+import astor  # type: ignore
+import nbconvert  # type: ignore
 import yaml
-from nbformat.notebooknode import NotebookNode
+from nbformat.notebooknode import NotebookNode  # type: ignore
 
 from .iotypes import CWLFilePathInput, CWLBooleanInput, CWLIntInput, CWLStringInput, CWLFilePathOutput, \
     CWLDumpableFile, CWLDumpableBinaryFile, CWLDumpable
@@ -30,7 +30,7 @@
 
 
 class AnnotatedVariablesExtractor(ast.NodeTransformer):
-    input_type_mapper = {
+    input_type_mapper: Dict[Tuple[str, ...], Tuple[str, str]] = {
         (CWLFilePathInput.__name__,): (
             'File',
             'pathlib.Path',
@@ -177,7 +177,7 @@ def visit_Import(self, node: ast.Import):
             return None
 
     def visit_ImportFrom(self, node: ast.ImportFrom) -> Any:
-        if node.module == 'ipython2cwl' or node.module.startswith('ipython2cwl.'):
+        if node.module == 'ipython2cwl' or (node.module is not None and node.module.startswith('ipython2cwl.')):
             return None
         return node
 
@@ -299,14 +299,18 @@ def compile(self, filename: Path = Path('notebookAsCWLTool.tar')) -> str:
         """
         workdir = tempfile.mkdtemp()
         script_path = os.path.join(workdir, 'notebookTool')
-        cwl_path = os.path.join(workdir, 'tool.cwl')
+        cwl_path: str = os.path.join(workdir, 'tool.cwl')
         dockerfile_path = os.path.join(workdir, 'Dockerfile')
         setup_path = os.path.join(workdir, 'setup.py')
         requirements_path = os.path.join(workdir, 'requirements.txt')
-        with open(script_path, 'wb') as f:
-            f.write(self._wrap_script_to_method(self._tree, self._variables).encode())
-        with open(cwl_path, 'w') as f:
-            yaml.safe_dump(self.cwl_command_line_tool(), f, encoding='utf-8')
+        with open(script_path, 'wb') as script_fd:
+            script_fd.write(self._wrap_script_to_method(self._tree, self._variables).encode())
+        with open(cwl_path, 'w') as cwl_fd:
+            yaml.safe_dump(
+                self.cwl_command_line_tool(),
+                cwl_fd,
+                encoding='utf-8'
+            )
         dockerfile = DOCKERFILE_TEMPLATE.format(
             python_version=f'python:{".".join(platform.python_version_tuple())}'
         )
diff --git a/ipython2cwl/repo2cwl.py b/ipython2cwl/repo2cwl.py
index 3a9ab37..417a082 100644
--- a/ipython2cwl/repo2cwl.py
+++ b/ipython2cwl/repo2cwl.py
@@ -9,11 +9,11 @@
 from typing import List, Optional, Tuple, Dict
 from urllib.parse import urlparse, ParseResult
 
-import git
-import nbformat
+import git  # type: ignore
+import nbformat  # type: ignore
 import yaml
 from git import Repo
-from repo2docker import Repo2Docker
+from repo2docker import Repo2Docker  # type: ignore
 
 from .cwltoolextractor import AnnotatedIPython2CWLToolConverter
 
@@ -68,8 +68,8 @@ def _store_jn_as_script(notebook_path: str, git_directory_absolute_path: str, bi
     return tool, script_relative_path
 
 
-def existing_path(path: str):
-    path = Path(path)
+def existing_path(path_str: str):
+    path: Path = Path(path_str)
     if not path.is_dir():
         raise argparse.ArgumentTypeError(f'Directory: {str(path)} does not exists')
     return path
@@ -159,7 +159,7 @@ def _repo2cwl(git_directory_path: Repo) -> Tuple[str, List[Dict]]:
             bin_path,
             r2d.output_image_spec
         )
-        if cwl_command_line_tool is None:
+        if cwl_command_line_tool is None or script_name is None:
             continue
         cwl_command_line_tool['baseCommand'] = os.path.join('/app', 'cwl', 'bin', script_name)
         tools.append(cwl_command_line_tool)
diff --git a/ipython2cwl/requirements_manager.py b/ipython2cwl/requirements_manager.py
index 1e828c5..1dee5a7 100644
--- a/ipython2cwl/requirements_manager.py
+++ b/ipython2cwl/requirements_manager.py
@@ -1,6 +1,6 @@
 from typing import List
 
-from pip._internal.operations import freeze
+from pip._internal.operations import freeze  # type: ignore
 
 
 class RequirementsManager:
diff --git a/test-requirements.txt b/test-requirements.txt
index 5896fc7..34e0730 100644
--- a/test-requirements.txt
+++ b/test-requirements.txt
@@ -6,3 +6,4 @@ gitpython>=3.1.3
 docker>=4.2.1
 git+https://github.com/giannisdoukas/cwltool.git#egg=cwltool
 pandas==1.0.5
+mypy
diff --git a/tests/repo-like/requirements.txt b/tests/repo-like/requirements.txt
index 3101697..7a997b5 100644
--- a/tests/repo-like/requirements.txt
+++ b/tests/repo-like/requirements.txt
@@ -1 +1 @@
-PyYAML==5.3.1
\ No newline at end of file
+PyYAML==5.3.1