diff --git a/src/flake8/main/application.py b/src/flake8/main/application.py
index 6e5373f..6393dad 100644
--- a/src/flake8/main/application.py
+++ b/src/flake8/main/application.py
@@ -97,8 +97,8 @@ class Application(object):
         #: The parsed diff information
         self.parsed_diff = {}  # type: Dict[str, Set[int]]
 
-    def parse_preliminary_options_and_args(self, argv=None):
-        # type: (Optional[List[str]]) -> None
+    def parse_preliminary_options_and_args(self, argv):
+        # type: (List[str]) -> None
         """Get preliminary options and args from CLI, pre-plugin-loading.
 
         We need to know the values of a few standard options and args now, so
@@ -121,7 +121,7 @@ class Application(object):
         # do not need to worry and we can continue. If it is, we successfully
         # defer printing the version until just a little bit later.
         # Similarly we have to defer printing the help text until later.
-        args = (argv if argv is not None else sys.argv)[:]
+        args = argv[:]
         try:
             args.remove("--version")
         except ValueError:
@@ -136,8 +136,8 @@ class Application(object):
             pass
 
         opts, args = self.option_manager.parse_known_args(args)
-        # parse_known_args includes program name and unknown options as args
-        args = [a for a in args[1:] if not a.startswith("-")]
+        # parse_known_args includes unknown options as args
+        args = [a for a in args if not a.startswith("-")]
         self.prelim_opts, self.prelim_args = opts, args
 
     def exit(self):
@@ -344,7 +344,7 @@ class Application(object):
         self.formatter.show_statistics(self.guide.stats)
 
     def initialize(self, argv):
-        # type: (Optional[List[str]]) -> None
+        # type: (List[str]) -> None
         """Initialize the application to be run.
 
         This finds the plugins, registers their options, and parses the
@@ -373,13 +373,13 @@ class Application(object):
         self.formatter.stop()
 
     def _run(self, argv):
-        # type: (Optional[List[str]]) -> None
+        # type: (List[str]) -> None
         self.initialize(argv)
         self.run_checks()
         self.report()
 
-    def run(self, argv=None):
-        # type: (Optional[List[str]]) -> None
+    def run(self, argv):
+        # type: (List[str]) -> None
         """Run our application.
 
         This method will also handle KeyboardInterrupt exceptions for the
diff --git a/src/flake8/main/cli.py b/src/flake8/main/cli.py
index 53f31e9..1bc9155 100644
--- a/src/flake8/main/cli.py
+++ b/src/flake8/main/cli.py
@@ -1,4 +1,5 @@
 """Command-line implementation of flake8."""
+import sys
 from typing import List, Optional
 
 from flake8.main import application
@@ -14,6 +15,9 @@ def main(argv=None):
     :param list argv:
         The arguments to be passed to the application for parsing.
     """
+    if argv is None:
+        argv = sys.argv[1:]
+
     app = application.Application()
     app.run(argv)
     app.exit()
diff --git a/tests/integration/test_main.py b/tests/integration/test_main.py
index 001f1ff..72e9621 100644
--- a/tests/integration/test_main.py
+++ b/tests/integration/test_main.py
@@ -126,3 +126,13 @@ def test_bug_report_successful(capsys):
     out, err = capsys.readouterr()
     assert json.loads(out)
     assert err == ''
+
+
+def test_obtaining_args_from_sys_argv_when_not_explicity_provided(capsys):
+    """Test that arguments are obtained from 'sys.argv'."""
+    with mock.patch('sys.argv', ['flake8', '--help']):
+        _call_main(None)
+
+    out, err = capsys.readouterr()
+    assert out.startswith('usage: flake8 [options] file file ...\n')
+    assert err == ''