diff --git a/.gitignore b/.gitignore
index fe89362..3e876ea 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,13 +1,14 @@
-*.pyc
-.tox
-.eggs
 *.egg
 *.egg-info
-build
-dist
+*.log
+*.pyc
+*.sw*
 *.zip
 .cache
-*.sw*
-*.log
-docs/build/html/*
 .coverage
+.eggs
+.tox
+/.mypy_cache
+build
+dist
+docs/build/html/*
diff --git a/mypy.ini b/mypy.ini
new file mode 100644
index 0000000..3d1cd43
--- /dev/null
+++ b/mypy.ini
@@ -0,0 +1,2 @@
+[mypy]
+ignore_missing_imports = true
diff --git a/setup.py b/setup.py
index cc5b872..528fc73 100644
--- a/setup.py
+++ b/setup.py
@@ -20,13 +20,14 @@ requires = [
     # And in which releases we will update those ranges here:
     # http://flake8.pycqa.org/en/latest/internal/releases.html#releasing-flake8
     "entrypoints >= 0.2.3, < 0.3.0",
-    "pyflakes >= 2.0.0, < 2.1.0",
+    "pyflakes >= 2.1.0, < 2.2.0",
     "pycodestyle >= 2.4.0, < 2.5.0",
     "mccabe >= 0.6.0, < 0.7.0",
 ]
 
 extras_require = {
     ":python_version<'3.4'": ['enum34'],
+    ":python_version<'3.5'": ['typing'],
     ":python_version<'3.2'": ['configparser'],
 }
 
diff --git a/src/flake8/checker.py b/src/flake8/checker.py
index b0e0644..ce33737 100644
--- a/src/flake8/checker.py
+++ b/src/flake8/checker.py
@@ -5,6 +5,7 @@ import logging
 import signal
 import sys
 import tokenize
+from typing import List, Optional  # noqa: F401 (until flake8 3.7)
 
 try:
     import multiprocessing
@@ -195,7 +196,7 @@ class Manager(object):
         )
 
     def make_checkers(self, paths=None):
-        # type: (List[str]) -> NoneType
+        # type: (List[str]) -> None
         """Create checkers for each file."""
         if paths is None:
             paths = self.arguments
@@ -411,7 +412,7 @@ class FileChecker(object):
             return None
 
     def report(self, error_code, line_number, column, text, line=None):
-        # type: (str, int, int, str) -> str
+        # type: (str, int, int, str, Optional[str]) -> str
         """Report an error by storing it in the results list."""
         if error_code is None:
             error_code, text = text.split(" ", 1)
diff --git a/src/flake8/main/application.py b/src/flake8/main/application.py
index ae33b13..86be4bd 100644
--- a/src/flake8/main/application.py
+++ b/src/flake8/main/application.py
@@ -4,6 +4,8 @@ from __future__ import print_function
 import logging
 import sys
 import time
+from typing import List, Optional, Sequence  # noqa: F401 (until flake8 3.7)
+from typing import Type, TYPE_CHECKING  # noqa: F401 (until flake8 3.7)
 
 import flake8
 from flake8 import checker
@@ -16,6 +18,12 @@ from flake8.options import aggregator, config
 from flake8.options import manager
 from flake8.plugins import manager as plugin_manager
 
+if TYPE_CHECKING:
+    # fmt: off
+    from flake8.formatting.base import BaseFormatter  # noqa: F401, E501 (until flake8 3.7)
+    # fmt: on
+
+
 LOG = logging.getLogger(__name__)
 
 
@@ -23,7 +31,7 @@ class Application(object):
     """Abstract our application into a class."""
 
     def __init__(self, program="flake8", version=flake8.__version__):
-        # type: (str, str) -> NoneType
+        # type: (str, str) -> None
         """Initialize our application.
 
         :param str program:
@@ -132,7 +140,7 @@ class Application(object):
         self.prelim_opts, self.prelim_args = opts, args
 
     def exit(self):
-        # type: () -> NoneType
+        # type: () -> None
         """Handle finalization and exiting the program.
 
         This should be the last thing called on the application instance. It
@@ -159,7 +167,7 @@ class Application(object):
             )
 
     def find_plugins(self):
-        # type: () -> NoneType
+        # type: () -> None
         """Find and load the plugins for this application.
 
         If :attr:`check_plugins`, or :attr:`formatting_plugins` are ``None``
@@ -191,14 +199,14 @@ class Application(object):
         self.formatting_plugins.load_plugins()
 
     def register_plugin_options(self):
-        # type: () -> NoneType
+        # type: () -> None
         """Register options provided by plugins to our option manager."""
         self.check_plugins.register_options(self.option_manager)
         self.check_plugins.register_plugin_versions(self.option_manager)
         self.formatting_plugins.register_options(self.option_manager)
 
     def parse_configuration_and_cli(self, argv=None):
-        # type: (Union[NoneType, List[str]]) -> NoneType
+        # type: (Optional[List[str]]) -> None
         """Parse configuration files and the CLI options.
 
         :param list argv:
@@ -238,7 +246,7 @@ class Application(object):
         return formatter_plugin.execute
 
     def make_formatter(self, formatter_class=None):
-        # type: () -> NoneType
+        # type: (Optional[Type[BaseFormatter]]) -> None
         """Initialize a formatter based on the parsed options."""
         if self.formatter is None:
             format_plugin = self.options.format
@@ -253,7 +261,7 @@ class Application(object):
             self.formatter = formatter_class(self.options)
 
     def make_guide(self):
-        # type: () -> NoneType
+        # type: () -> None
         """Initialize our StyleGuide."""
         if self.guide is None:
             self.guide = style_guide.StyleGuideManager(
@@ -264,7 +272,7 @@ class Application(object):
             self.guide.add_diff_ranges(self.parsed_diff)
 
     def make_file_checker_manager(self):
-        # type: () -> NoneType
+        # type: () -> None
         """Initialize our FileChecker Manager."""
         if self.file_checker_manager is None:
             self.file_checker_manager = checker.Manager(
@@ -274,7 +282,7 @@ class Application(object):
             )
 
     def run_checks(self, files=None):
-        # type: (Union[List[str], NoneType]) -> NoneType
+        # type: (Optional[List[str]]) -> None
         """Run the actual checks with the FileChecker Manager.
 
         This method encapsulates the logic to make a
@@ -315,7 +323,7 @@ class Application(object):
         self.formatter.show_benchmarks(statistics)
 
     def report_errors(self):
-        # type: () -> NoneType
+        # type: () -> None
         """Report all the errors found by flake8 3.0.
 
         This also updates the :attr:`result_count` attribute with the total
@@ -338,7 +346,7 @@ class Application(object):
         self.formatter.show_statistics(self.guide.stats)
 
     def initialize(self, argv):
-        # type: () -> NoneType
+        # type: (Sequence[str]) -> None
         """Initialize the application to be run.
 
         This finds the plugins, registers their options, and parses the
@@ -367,13 +375,13 @@ class Application(object):
         self.formatter.stop()
 
     def _run(self, argv):
-        # type: (Union[NoneType, List[str]]) -> NoneType
+        # type: (Optional[List[str]]) -> None
         self.initialize(argv)
         self.run_checks()
         self.report()
 
     def run(self, argv=None):
-        # type: (Union[NoneType, List[str]]) -> NoneType
+        # type: (Optional[List[str]]) -> None
         """Run our application.
 
         This method will also handle KeyboardInterrupt exceptions for the
@@ -389,7 +397,7 @@ class Application(object):
             self.catastrophic_failure = True
         except exceptions.ExecutionError as exc:
             print("There was a critical error during execution of Flake8:")
-            print(exc.message)
+            print(exc)
             LOG.exception(exc)
             self.catastrophic_failure = True
         except exceptions.EarlyQuit:
diff --git a/src/flake8/main/cli.py b/src/flake8/main/cli.py
index 8ba6288..d6cb933 100644
--- a/src/flake8/main/cli.py
+++ b/src/flake8/main/cli.py
@@ -1,9 +1,11 @@
 """Command-line implementation of flake8."""
+from typing import List, Optional  # noqa: F401 (until flake8 3.7)
+
 from flake8.main import application
 
 
 def main(argv=None):
-    # type: (Union[NoneType, List[str]]) -> NoneType
+    # type: (Optional[List[str]]) -> None
     """Execute the main bit of the application.
 
     This handles the creation of an instance of :class:`Application`, runs it,
diff --git a/src/flake8/main/setuptools_command.py b/src/flake8/main/setuptools_command.py
index 0a76057..a3ccf03 100644
--- a/src/flake8/main/setuptools_command.py
+++ b/src/flake8/main/setuptools_command.py
@@ -1,5 +1,6 @@
 """The logic for Flake8's integration with setuptools."""
 import os
+from typing import List  # noqa: F401 (until flake8 3.7)
 
 import setuptools
 
@@ -19,7 +20,7 @@ class Flake8(setuptools.Command):
     # of options, and since this will break when users use plugins that
     # provide command-line options, we are leaving this empty. If users want
     # to configure this command, they can do so through config files.
-    user_options = []
+    user_options = []  # type: List[str]
 
     def initialize_options(self):
         """Override this method to initialize our application."""
diff --git a/src/flake8/plugins/manager.py b/src/flake8/plugins/manager.py
index 045cfd7..28b4b35 100644
--- a/src/flake8/plugins/manager.py
+++ b/src/flake8/plugins/manager.py
@@ -315,7 +315,7 @@ class PluginManager(object):  # pylint: disable=too-few-public-methods
 
 
 def version_for(plugin):
-    # (Plugin) -> Union[str, NoneType]
+    # (Plugin) -> Optional[str]
     """Determine the version of a plugin by its module.
 
     :param plugin:
diff --git a/src/flake8/plugins/pyflakes.py b/src/flake8/plugins/pyflakes.py
index 880373a..4435380 100644
--- a/src/flake8/plugins/pyflakes.py
+++ b/src/flake8/plugins/pyflakes.py
@@ -30,6 +30,8 @@ FLAKE8_PYFLAKES_CODES = {
     "TooManyExpressionsInStarredAssignment": "F621",
     "TwoStarredExpressions": "F622",
     "AssertTuple": "F631",
+    "IsLiteral": "F632",
+    "InvalidPrintSyntax": "F633",
     "BreakOutsideLoop": "F701",
     "ContinueOutsideLoop": "F702",
     "ContinueInFinally": "F703",
@@ -39,6 +41,7 @@ FLAKE8_PYFLAKES_CODES = {
     "DefaultExceptNotLast": "F707",
     "DoctestSyntaxError": "F721",
     "ForwardAnnotationSyntaxError": "F722",
+    "CommentAnnotationSyntaxError": "F723",
     "RedefinedWhileUnused": "F811",
     "RedefinedInListComp": "F812",
     "UndefinedName": "F821",
@@ -72,7 +75,7 @@ class FlakesChecker(pyflakes.checker.Checker):
     include_in_doctest = []
     exclude_from_doctest = []
 
-    def __init__(self, tree, filename):
+    def __init__(self, tree, file_tokens, filename):
         """Initialize the PyFlakes plugin with an AST tree and filename."""
         filename = utils.normalize_paths(filename)[0]
         with_doctest = self.with_doctest
@@ -97,7 +100,10 @@ class FlakesChecker(pyflakes.checker.Checker):
                     with_doctest = True
 
         super(FlakesChecker, self).__init__(
-            tree, filename=filename, withDoctest=with_doctest
+            tree,
+            filename=filename,
+            withDoctest=with_doctest,
+            file_tokens=file_tokens,
         )
 
     @classmethod
diff --git a/src/flake8/processor.py b/src/flake8/processor.py
index c31a5c4..47f5cd2 100644
--- a/src/flake8/processor.py
+++ b/src/flake8/processor.py
@@ -3,6 +3,7 @@ import contextlib
 import logging
 import sys
 import tokenize
+from typing import List  # noqa: F401 (until flake8 3.7)
 
 import flake8
 from flake8 import defaults
@@ -348,7 +349,7 @@ class FileProcessor(object):
             return False
 
     def strip_utf_bom(self):
-        # type: () -> NoneType
+        # type: () -> None
         """Strip the UTF bom from the lines of the file."""
         if not self.lines:
             # If we have nothing to analyze quit early
diff --git a/src/flake8/style_guide.py b/src/flake8/style_guide.py
index 01d85d7..4626fd6 100644
--- a/src/flake8/style_guide.py
+++ b/src/flake8/style_guide.py
@@ -7,6 +7,7 @@ import functools
 import itertools
 import linecache
 import logging
+from typing import Optional, Union  # noqa: F401 (until flake8 3.7)
 
 from flake8 import defaults
 from flake8 import statistics
@@ -391,7 +392,7 @@ class StyleGuideManager(object):
         text,
         physical_line=None,
     ):
-        # type: (str, str, int, int, str) -> int
+        # type: (str, str, int, int, str, Optional[str]) -> int
         """Handle an error reported by a check.
 
         :param str code:
@@ -511,7 +512,7 @@ class StyleGuide(object):
         text,
         physical_line=None,
     ):
-        # type: (str, str, int, int, str) -> int
+        # type: (str, str, int, int, str, Optional[str]) -> int
         """Handle an error reported by a check.
 
         :param str code:
diff --git a/src/flake8/utils.py b/src/flake8/utils.py
index 0c97a39..502e1ca 100644
--- a/src/flake8/utils.py
+++ b/src/flake8/utils.py
@@ -8,6 +8,13 @@ import platform
 import re
 import sys
 import tokenize
+from typing import Callable, Dict, Generator  # noqa: F401 (until flake8 3.7)
+from typing import List, Pattern, Sequence  # noqa: F401 (until flake8 3,7)
+from typing import Tuple, TYPE_CHECKING  # noqa: F401 (until flake8 3.7)
+from typing import Union  # noqa: F401 (until flake8 3.7)
+
+if TYPE_CHECKING:
+    from flake8.plugins.manager import Plugin  # noqa: F401 (until flake8 3.7)
 
 DIFF_HUNK_REGEXP = re.compile(r"^@@ -\d+(?:,\d+)? \+(\d+)(?:,(\d+))? @@.*$")
 COMMA_SEPARATED_LIST_RE = re.compile(r"[,\s]")
@@ -15,7 +22,7 @@ LOCAL_PLUGIN_LIST_RE = re.compile(r"[,\t\n\r\f\v]")
 
 
 def parse_comma_separated_list(value, regexp=COMMA_SEPARATED_LIST_RE):
-    # type: (Union[Sequence[str], str]) -> List[str]
+    # type: (Union[Sequence[str], str], Pattern[str]) -> List[str]
     """Parse a comma-separated list.
 
     :param value:
@@ -321,7 +328,7 @@ def _default_predicate(*args):
 
 
 def filenames_from(arg, predicate=None):
-    # type: (str, callable) -> Generator
+    # type: (str, Callable[[str], bool]) -> Generator
     """Generate filenames from an argument.
 
     :param str arg:
@@ -382,7 +389,7 @@ def fnmatch(filename, patterns, default=True):
 
 
 def parameters_for(plugin):
-    # type: (flake8.plugins.manager.Plugin) -> Dict[str, bool]
+    # type: (Plugin) -> Dict[str, bool]
     """Return the parameters for the plugin.
 
     This will inspect the plugin and return either the function parameters
diff --git a/tox.ini b/tox.ini
index ae0545f..5d94e5c 100644
--- a/tox.ini
+++ b/tox.ini
@@ -74,9 +74,9 @@ commands =
 basepython = python3
 skip_install = true
 deps =
-    mypy-lang
+    mypy
 commands =
-    mypy flake8
+    mypy src
 
 [testenv:bandit]
 basepython = python3