diff --git a/misc/actions_stubs.py b/misc/actions_stubs.py
new file mode 100644
index 000000000000..978af7187ffe
--- /dev/null
+++ b/misc/actions_stubs.py
@@ -0,0 +1,111 @@
+#!/usr/bin/env python3
+import os
+import shutil
+from typing import Tuple, Any
+try:
+    import click
+except ImportError:
+    print("You need the module \'click\'")
+    exit(1)
+
+base_path = os.getcwd()
+
+# I don't know how to set callables with different args
+def apply_all(func: Any, directory: str, extension: str,
+            to_extension: str='', exclude: Tuple[str]=('',),
+            recursive: bool=True, debug: bool=False) -> None:
+    excluded = [x+extension for x in exclude] if exclude else []
+    for p, d, files in os.walk(os.path.join(base_path,directory)):
+        for f in files:
+            if "{}".format(f) in excluded:
+                continue
+            inner_path = os.path.join(p,f)
+            if not inner_path.endswith(extension):
+                continue
+            if to_extension:
+                new_path = "{}{}".format(inner_path[:-len(extension)],to_extension)
+                func(inner_path,new_path)
+            else:
+                func(inner_path)
+        if not recursive:
+            break
+
+def confirm(resp: bool=False, **kargs) -> bool:
+    kargs['rest'] = "to this {f2}/*{e2}".format(**kargs) if kargs.get('f2') else ''
+    prompt = "{act} all files {rec}matching this expression {f1}/*{e1} {rest}".format(**kargs)
+    prompt.format(**kargs)
+    prompt = "{} [{}]|{}: ".format(prompt, 'Y' if resp else 'N', 'n' if resp else 'y')
+    while True:
+        ans = input(prompt).lower()
+        if not ans:
+            return resp
+        if ans not in ['y','n']:
+            print( 'Please, enter (y) or (n).')
+            continue
+        if ans == 'y':
+            return True
+        else:
+            return False
+
+actions = ['cp', 'mv', 'rm']
+@click.command(context_settings=dict(help_option_names=['-h', '--help']))
+@click.option('--action', '-a', type=click.Choice(actions), required=True, help="What do I have to do :-)")
+@click.option('--dir', '-d', 'directory', default='stubs', help="Directory to start search!")
+@click.option('--ext', '-e', 'extension', default='.py', help="Extension \"from\" will be applied the action. Default .py")
+@click.option('--to', '-t', 'to_extension', default='.pyi', help="Extension \"to\" will be applied the action if can. Default .pyi")
+@click.option('--exclude', '-x', multiple=True, default=('__init__',), help="For every appear, will ignore this files. (can set multiples times)")
+@click.option('--not-recursive', '-n', default=True, is_flag=True, help="Set if don't want to walk recursively.")
+def main(action: str, directory: str, extension: str, to_extension: str,
+    exclude: Tuple[str], not_recursive: bool) -> None:
+    """
+    This script helps to copy/move/remove files based on their extension.
+
+    The three actions will ask you for confirmation.
+
+    Examples (by default the script search in stubs directory):
+
+    - Change extension of all stubs from .py to .pyi:
+
+        python <script.py> -a mv
+
+    - Revert the previous action.
+
+        python <script.py> -a mv -e .pyi -t .py
+
+    - If you want to ignore "awesome.py" files.
+
+        python <script.py> -a [cp|mv|rm] -x awesome
+
+    - If you want to ignore "awesome.py" and "__init__.py" files.
+
+        python <script.py> -a [cp|mv|rm] -x awesome -x __init__
+
+    - If you want to remove all ".todo" files in "todo" directory, but not recursively:
+
+        python <script.py> -a rm -e .todo -d todo -r
+
+    """
+    if action not in actions:
+        print("Your action have to be one of this: {}".format(', '.join(actions)))
+        return
+
+    rec = "[Recursively] " if not_recursive else ''
+    if not extension.startswith('.'):
+        extension = ".{}".format(extension)
+    if not to_extension.startswith('.'):
+        to_extension = ".{}".format(to_extension)
+    if directory.endswith('/'):
+        directory = directory[:-1]
+    if action == 'cp':
+        if confirm(act='Copy',rec=rec, f1=directory, e1=extension, f2=directory, e2=to_extension):
+            apply_all(shutil.copy, directory, extension, to_extension, exclude, not_recursive)
+    elif action == 'rm':
+        if confirm(act='Remove',rec=rec, f1=directory, e1=extension):
+            apply_all(os.remove, directory, extension, exclude=exclude, recursive=not_recursive)
+    elif action == 'mv':
+        if confirm(act='Move',rec=rec, f1=directory, e1=extension, f2=directory, e2=to_extension):
+            apply_all(shutil.move, directory, extension, to_extension, exclude, not_recursive)
+
+
+if __name__ == '__main__':
+    main()
diff --git a/mypy/build.py b/mypy/build.py
index 1d515ac9caeb..19dfc88c70eb 100644
--- a/mypy/build.py
+++ b/mypy/build.py
@@ -42,7 +42,6 @@
 MODULE = 'module'                # Build/run module as a script
 TEST_BUILTINS = 'test-builtins'  # Use stub builtins to speed up tests
 
-
 # State ids. These describe the states a source file / module can be in a
 # build.
 
@@ -228,6 +227,7 @@ def default_lib_path(data_dir: str, target: int, pyversion: int,
 
 
 def lookup_program(module: str, lib_path: List[str]) -> str:
+    # Modules are .py and not .pyi
     path = find_module(module, lib_path)
     if path:
         return path
@@ -856,14 +856,16 @@ def read_module_source_from_file(id: str,
 
 def find_module(id: str, lib_path: List[str]) -> str:
     """Return the path of the module source file, or None if not found."""
+    extensions = ['.pyi', '.py']
     for pathitem in lib_path:
-        comp = id.split('.')
-        path = os.path.join(pathitem, os.sep.join(comp[:-1]), comp[-1] + '.py')
-        text = ''
-        if not os.path.isfile(path):
-            path = os.path.join(pathitem, os.sep.join(comp), '__init__.py')
-        if os.path.isfile(path) and verify_module(id, path):
-            return path
+        for extension in extensions:
+            comp = id.split('.')
+            path = os.path.join(pathitem, os.sep.join(comp[:-1]), comp[-1] + extension)
+            text = ''
+            if not os.path.isfile(path):
+                path = os.path.join(pathitem, os.sep.join(comp), '__init__.py')
+            if os.path.isfile(path) and verify_module(id, path):
+                return path
     return None
 
 
diff --git a/mypy/test/data/check-modules.test b/mypy/test/data/check-modules.test
index b021a44f1ced..45a5dd17e05a 100644
--- a/mypy/test/data/check-modules.test
+++ b/mypy/test/data/check-modules.test
@@ -1,3 +1,4 @@
+
 -- Test cases for the type checker.
 
 [case testAccessImportedDefinitions]
@@ -137,6 +138,24 @@ def f() -> None: pass
 [out]
 main: In class "C":
 
+[case testImportWithStub]
+import _m
+_m.f("hola")
+[file _m.pyi]
+def f(c:str) -> None: pass
+[out]
+
+
+[case testImportWithStubIncompatibleType]
+import _m
+_m.f("hola")
+_m.f(12)  # E: Argument 1 to "f" has incompatible type "int"; expected "str"
+[file _m.py]
+def f(c):
+  print(c)
+[file _m.pyi]
+def f(c:str) -> None: pass
+
 [case testInvalidOperationsOnModules]
 import m
 import typing
diff --git a/setup.py b/setup.py
index aacd85951c4c..d88e9cb16ef5 100644
--- a/setup.py
+++ b/setup.py
@@ -34,6 +34,7 @@
     for stub_dir in stub_dirs:
         target = os.path.join('lib', 'mypy', 'stubs', py_version, stub_dir)
         files = glob.glob(os.path.join(base, stub_dir, '*.py'))
+        files += glob.glob(os.path.join(base, stub_dir, '*.pyi'))
         stubs.append((target, files))
 
 classifiers = [
diff --git a/travis.sh b/travis.sh
old mode 100644
new mode 100755