diff --git a/setup.cfg b/setup.cfg
index cb6d790a961..cd5a2b256d6 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -26,81 +26,6 @@ ignore = W504
 follow_imports = silent
 ignore_missing_imports = True
 
-[mypy-pip/_internal/build_env]
-strict_optional = False
-
-[mypy-pip/_internal/cache]
-strict_optional = False
-
-[mypy-pip/_internal/cli/base_command]
-strict_optional = False
-
-[mypy-pip/_internal/cli/cmdoptions]
-strict_optional = False
-
-[mypy-pip/_internal/configuration]
-strict_optional = False
-
-[mypy-pip/_internal/index]
-strict_optional = False
-
-[mypy-pip/_internal/legacy_resolve]
-strict_optional = False
-
-[mypy-pip/_internal/locations]
-strict_optional = False
-
-[mypy-pip/_internal/models/format_control]
-strict_optional = False
-
-[mypy-pip/_internal/operations/check]
-strict_optional = False
-
-[mypy-pip/_internal/operations/freeze]
-strict_optional = False
-
-[mypy-pip/_internal/operations/prepare]
-strict_optional = False
-
-[mypy-pip/_internal/pep425tags]
-strict_optional = False
-
-[mypy-pip/_internal/req/*]
-disallow_untyped_defs = True
-
-[mypy-pip/_internal/req]
-strict_optional = False
-
-[mypy-pip/_internal/req/constructors]
-strict_optional = False
-
-[mypy-pip/_internal/req/req_file]
-strict_optional = False
-
-[mypy-pip/_internal/req/req_install]
-strict_optional = False
-
-[mypy-pip/_internal/req/req_set]
-strict_optional = False
-
-[mypy-pip/_internal/req/req_tracker]
-strict_optional = False
-
-[mypy-pip/_internal/utils/encoding]
-strict_optional = False
-
-[mypy-pip/_internal/utils/glibc]
-strict_optional = False
-
-[mypy-pip/_internal/utils/misc]
-strict_optional = False
-
-[mypy-pip/_internal/utils/ui]
-strict_optional = False
-
-[mypy-pip/_internal/wheel]
-strict_optional = False
-
 [mypy-pip/_vendor/*]
 follow_imports = skip
 ignore_errors = True
diff --git a/src/pip/_internal/build_env.py b/src/pip/_internal/build_env.py
index a060ceea2ca..5decc91050e 100644
--- a/src/pip/_internal/build_env.py
+++ b/src/pip/_internal/build_env.py
@@ -1,6 +1,9 @@
 """Build Environment used for isolation during sdist building
 """
 
+# The following comment should be removed at some point in the future.
+# mypy: strict-optional=False
+
 import logging
 import os
 import sys
diff --git a/src/pip/_internal/cache.py b/src/pip/_internal/cache.py
index 894624c1dbc..0e893cd45a7 100644
--- a/src/pip/_internal/cache.py
+++ b/src/pip/_internal/cache.py
@@ -1,6 +1,9 @@
 """Cache Management
 """
 
+# The following comment should be removed at some point in the future.
+# mypy: strict-optional=False
+
 import errno
 import hashlib
 import logging
diff --git a/src/pip/_internal/cli/base_command.py b/src/pip/_internal/cli/base_command.py
index fd771b1412c..2ba19f944b0 100644
--- a/src/pip/_internal/cli/base_command.py
+++ b/src/pip/_internal/cli/base_command.py
@@ -1,4 +1,8 @@
 """Base Command class, and related routines"""
+
+# The following comment should be removed at some point in the future.
+# mypy: strict-optional=False
+
 from __future__ import absolute_import, print_function
 
 import logging
diff --git a/src/pip/_internal/cli/cmdoptions.py b/src/pip/_internal/cli/cmdoptions.py
index ecf4d20bcd6..ea4d4de5cb1 100644
--- a/src/pip/_internal/cli/cmdoptions.py
+++ b/src/pip/_internal/cli/cmdoptions.py
@@ -5,8 +5,11 @@
 globally. One reason being that options with action='append' can carry state
 between parses. pip parses general options twice internally, and shouldn't
 pass on state. To be consistent, all options will follow this design.
-
 """
+
+# The following comment should be removed at some point in the future.
+# mypy: strict-optional=False
+
 from __future__ import absolute_import
 
 import logging
diff --git a/src/pip/_internal/configuration.py b/src/pip/_internal/configuration.py
index 10edb4829ab..6843557855f 100644
--- a/src/pip/_internal/configuration.py
+++ b/src/pip/_internal/configuration.py
@@ -11,6 +11,9 @@
   A single word describing where the configuration key-value pair came from
 """
 
+# The following comment should be removed at some point in the future.
+# mypy: strict-optional=False
+
 import locale
 import logging
 import os
diff --git a/src/pip/_internal/index.py b/src/pip/_internal/index.py
index 75fd4e005ff..c5bc3bc3428 100644
--- a/src/pip/_internal/index.py
+++ b/src/pip/_internal/index.py
@@ -1,4 +1,8 @@
 """Routines related to PyPI, indexes"""
+
+# The following comment should be removed at some point in the future.
+# mypy: strict-optional=False
+
 from __future__ import absolute_import
 
 import cgi
diff --git a/src/pip/_internal/legacy_resolve.py b/src/pip/_internal/legacy_resolve.py
index 2f629b39d11..f52db418b21 100644
--- a/src/pip/_internal/legacy_resolve.py
+++ b/src/pip/_internal/legacy_resolve.py
@@ -10,6 +10,9 @@
     a. "first found, wins" (where the order is breadth first)
 """
 
+# The following comment should be removed at some point in the future.
+# mypy: strict-optional=False
+
 import logging
 import sys
 from collections import defaultdict
diff --git a/src/pip/_internal/locations.py b/src/pip/_internal/locations.py
index 5f843d797c4..7fbc0ad8907 100644
--- a/src/pip/_internal/locations.py
+++ b/src/pip/_internal/locations.py
@@ -1,4 +1,8 @@
 """Locations where we look for configs, install stuff, etc"""
+
+# The following comment should be removed at some point in the future.
+# mypy: strict-optional=False
+
 from __future__ import absolute_import
 
 import os
diff --git a/src/pip/_internal/models/format_control.py b/src/pip/_internal/models/format_control.py
index 53138e48eca..c08c30f83f9 100644
--- a/src/pip/_internal/models/format_control.py
+++ b/src/pip/_internal/models/format_control.py
@@ -1,3 +1,6 @@
+# The following comment should be removed at some point in the future.
+# mypy: strict-optional=False
+
 from pip._vendor.packaging.utils import canonicalize_name
 
 from pip._internal.utils.typing import MYPY_CHECK_RUNNING
diff --git a/src/pip/_internal/operations/check.py b/src/pip/_internal/operations/check.py
index 7b8b369fc90..3bc9f8107ea 100644
--- a/src/pip/_internal/operations/check.py
+++ b/src/pip/_internal/operations/check.py
@@ -1,6 +1,9 @@
 """Validation of dependencies of packages
 """
 
+# The following comment should be removed at some point in the future.
+# mypy: strict-optional=False
+
 import logging
 from collections import namedtuple
 
diff --git a/src/pip/_internal/operations/freeze.py b/src/pip/_internal/operations/freeze.py
index b4193730a03..6eaa85b19ec 100644
--- a/src/pip/_internal/operations/freeze.py
+++ b/src/pip/_internal/operations/freeze.py
@@ -1,3 +1,6 @@
+# The following comment should be removed at some point in the future.
+# mypy: strict-optional=False
+
 from __future__ import absolute_import
 
 import collections
diff --git a/src/pip/_internal/operations/prepare.py b/src/pip/_internal/operations/prepare.py
index 471a60ce828..2449e8efc28 100644
--- a/src/pip/_internal/operations/prepare.py
+++ b/src/pip/_internal/operations/prepare.py
@@ -1,6 +1,9 @@
 """Prepares a distribution for installation
 """
 
+# The following comment should be removed at some point in the future.
+# mypy: strict-optional=False
+
 import logging
 import os
 
diff --git a/src/pip/_internal/req/__init__.py b/src/pip/_internal/req/__init__.py
index c39f63fa831..9955a716ce2 100644
--- a/src/pip/_internal/req/__init__.py
+++ b/src/pip/_internal/req/__init__.py
@@ -1,3 +1,6 @@
+# The following comment should be removed at some point in the future.
+# mypy: strict-optional=False
+
 from __future__ import absolute_import
 
 import logging
diff --git a/src/pip/_internal/req/constructors.py b/src/pip/_internal/req/constructors.py
index cd0ab504282..28cef933221 100644
--- a/src/pip/_internal/req/constructors.py
+++ b/src/pip/_internal/req/constructors.py
@@ -8,6 +8,9 @@
 InstallRequirement.
 """
 
+# The following comment should be removed at some point in the future.
+# mypy: strict-optional=False
+
 import logging
 import os
 import re
diff --git a/src/pip/_internal/req/req_file.py b/src/pip/_internal/req/req_file.py
index 3e39f9603ed..65772b20a83 100644
--- a/src/pip/_internal/req/req_file.py
+++ b/src/pip/_internal/req/req_file.py
@@ -2,6 +2,9 @@
 Requirements file parsing
 """
 
+# The following comment should be removed at some point in the future.
+# mypy: strict-optional=False
+
 from __future__ import absolute_import
 
 import optparse
diff --git a/src/pip/_internal/req/req_install.py b/src/pip/_internal/req/req_install.py
index 9c0e69a0bd7..4752fa88816 100644
--- a/src/pip/_internal/req/req_install.py
+++ b/src/pip/_internal/req/req_install.py
@@ -1,3 +1,6 @@
+# The following comment should be removed at some point in the future.
+# mypy: strict-optional=False
+
 from __future__ import absolute_import
 
 import logging
diff --git a/src/pip/_internal/req/req_set.py b/src/pip/_internal/req/req_set.py
index d1966a4aa9c..0b81ed215b0 100644
--- a/src/pip/_internal/req/req_set.py
+++ b/src/pip/_internal/req/req_set.py
@@ -1,3 +1,6 @@
+# The following comment should be removed at some point in the future.
+# mypy: strict-optional=False
+
 from __future__ import absolute_import
 
 import logging
diff --git a/src/pip/_internal/req/req_tracker.py b/src/pip/_internal/req/req_tracker.py
index e36a3f6b5c2..bef30f236af 100644
--- a/src/pip/_internal/req/req_tracker.py
+++ b/src/pip/_internal/req/req_tracker.py
@@ -1,3 +1,6 @@
+# The following comment should be removed at some point in the future.
+# mypy: strict-optional=False
+
 from __future__ import absolute_import
 
 import contextlib
diff --git a/src/pip/_internal/utils/encoding.py b/src/pip/_internal/utils/encoding.py
index 30139f2e591..ab4d4b98e3e 100644
--- a/src/pip/_internal/utils/encoding.py
+++ b/src/pip/_internal/utils/encoding.py
@@ -1,3 +1,6 @@
+# The following comment should be removed at some point in the future.
+# mypy: strict-optional=False
+
 import codecs
 import locale
 import re
diff --git a/src/pip/_internal/utils/glibc.py b/src/pip/_internal/utils/glibc.py
index aa77d9b60f8..544b4c2792b 100644
--- a/src/pip/_internal/utils/glibc.py
+++ b/src/pip/_internal/utils/glibc.py
@@ -1,3 +1,6 @@
+# The following comment should be removed at some point in the future.
+# mypy: strict-optional=False
+
 from __future__ import absolute_import
 
 import os
diff --git a/src/pip/_internal/utils/misc.py b/src/pip/_internal/utils/misc.py
index a08669a4b85..33b0653a0a8 100644
--- a/src/pip/_internal/utils/misc.py
+++ b/src/pip/_internal/utils/misc.py
@@ -1,3 +1,6 @@
+# The following comment should be removed at some point in the future.
+# mypy: strict-optional=False
+
 from __future__ import absolute_import
 
 import contextlib
diff --git a/src/pip/_internal/utils/ui.py b/src/pip/_internal/utils/ui.py
index 46390f4a598..80cdab37912 100644
--- a/src/pip/_internal/utils/ui.py
+++ b/src/pip/_internal/utils/ui.py
@@ -1,3 +1,6 @@
+# The following comment should be removed at some point in the future.
+# mypy: strict-optional=False
+
 from __future__ import absolute_import, division
 
 import contextlib
diff --git a/src/pip/_internal/wheel.py b/src/pip/_internal/wheel.py
index b59094fdfbd..35c73210bbf 100644
--- a/src/pip/_internal/wheel.py
+++ b/src/pip/_internal/wheel.py
@@ -1,6 +1,10 @@
 """
 Support for installing and building the "wheel" binary package format.
 """
+
+# The following comment should be removed at some point in the future.
+# mypy: strict-optional=False
+
 from __future__ import absolute_import
 
 import collections