diff --git a/src/pipupgrade/_pip.py b/src/pipupgrade/_pip.py
index d8970a7..212a4d4 100644
--- a/src/pipupgrade/_pip.py
+++ b/src/pipupgrade/_pip.py
@@ -5,6 +5,7 @@
 import pip
 import json
 import os.path as osp
+from typing import List
 
 # imports - module imports
 from pipupgrade.util.system  import which, popen
@@ -15,16 +16,34 @@
 
 logger = get_logger()
 
-PIP9 = int(pip.__version__.split(".")[0]) < 10
+MAJOR_VERSION = int(pip.__version__.split(".")[0])
 
-if PIP9:
-    # from pip                 import get_installed_distributions
-    from pip.req             import parse_requirements
-    from pip.req.req_install import InstallRequirement
-else:
+if MAJOR_VERSION >= 20:
+    from pip._internal.req.constructors import install_req_from_parsed_requirement
+    from pip._internal.req.req_file import (
+        parse_requirements as _real_parse_requirements,
+    )
+    from pip._internal.req.req_install import InstallRequirement
+
+    def parse_requirements(
+        filename, session
+    ):  # type: (str, str) -> List[InstallRequirement]
+        """Wrap pip internal `parse_requirements`, which now returns
+        `ParsedRequirement` instances, to instead return `InstallRequirement`-
+        as with the previous implementation
+        Based on https://github.com/pypa/pip/blob/a48ad5385b234097d51283b08c3d933fd81ef534/tests/unit/test_req_file.py#L50"""
+        for parsed_req in _real_parse_requirements(filename, session):
+            yield install_req_from_parsed_requirement(parsed_req)
+
+
+elif MAJOR_VERSION >= 10:
     # from pip._internal.utils.misc      import get_installed_distributions
-    from pip._internal.req             import parse_requirements
+    from pip._internal.req import parse_requirements
     from pip._internal.req.req_install import InstallRequirement
+else:
+    # from pip                 import get_installed_distributions
+    from pip.req import parse_requirements
+    from pip.req.req_install import InstallRequirement
 
 from pip._vendor.pkg_resources import (
     Distribution,
diff --git a/tests/pipupgrade/test__pip.py b/tests/pipupgrade/test__pip.py
index 8c82e75..0688079 100644
--- a/tests/pipupgrade/test__pip.py
+++ b/tests/pipupgrade/test__pip.py
@@ -2,10 +2,10 @@
 from __future__ import absolute_import
 
 # imports - standard imports
-import subprocess
+import os
 
 # imports - test imports
-import pytest
+from testutils import PATH
 
 # imports - module imports
 from pipupgrade         import _pip
@@ -43,8 +43,17 @@ def _assert_outerr(routerr, outerr):
 
     _pip.call("install", "pipupgrade")
     assert_pip_call(_pip.call("install", "pipupgrade", quiet = True))
-    
+
     _pip.call("install", "pipupgrade", log = path)
     assert tempfile.read()
 
-    # assert_pip_call(_pip.call("list", output = True))
\ No newline at end of file
+    # assert_pip_call(_pip.call("list", output = True))
+
+
+def test_parse_requirements():
+    """`parse_requirements` returns an iterable of `InstallRequirement`"""
+    filepath = os.path.join(PATH["DATA"], "project", "requirements.txt")
+
+    requirements = list(_pip.parse_requirements(filepath, session="hack"))
+
+    assert all([isinstance(req, _pip.InstallRequirement) for req in requirements])