diff --git a/NEWS.rst b/NEWS.rst
index 0786b15..6f0abb0 100644
--- a/NEWS.rst
+++ b/NEWS.rst
@@ -5,7 +5,9 @@ Version history
 0.0.7   (unreleased)
 ====================
 
-- Nothing yet.
+- tox plugin: Work around https://github.com/tox-dev/tox/issues/2372 by
+  telling ``tox`` to pass through lower-case ``http_proxy`` and
+  ``https_proxy`` environment variables.
 
 0.0.6   (2022-04-05)
 ====================
diff --git a/lpcraft/plugin/tests/test_plugins.py b/lpcraft/plugin/tests/test_plugins.py
index d8872a5..f7c2012 100644
--- a/lpcraft/plugin/tests/test_plugins.py
+++ b/lpcraft/plugin/tests/test_plugins.py
@@ -60,7 +60,7 @@ def test_tox_plugin(self, mock_get_host_architecture, mock_get_provider):
                         "apache2",
                     ],
                     cwd=PosixPath("/root/project"),
-                    env={"PLUGIN": "tox"},
+                    env={"TOX_TESTENV_PASSENV": "http_proxy https_proxy"},
                     stdout=ANY,
                     stderr=ANY,
                 ),
@@ -73,7 +73,7 @@ def test_tox_plugin(self, mock_get_host_architecture, mock_get_provider):
                         "python3 -m pip install tox==3.24.5; tox",
                     ],
                     cwd=PosixPath("/root/project"),
-                    env={"PLUGIN": "tox"},
+                    env={"TOX_TESTENV_PASSENV": "http_proxy https_proxy"},
                     stdout=ANY,
                     stderr=ANY,
                 ),
@@ -152,14 +152,14 @@ def test_run_command_from_configuration_takes_precedence(
                         "apache2",
                     ],
                     cwd=PosixPath("/root/project"),
-                    env={"PLUGIN": "tox"},
+                    env={"TOX_TESTENV_PASSENV": "http_proxy https_proxy"},
                     stdout=ANY,
                     stderr=ANY,
                 ),
                 call(
                     ["bash", "--noprofile", "--norc", "-ec", "ls"],
                     cwd=PosixPath("/root/project"),
-                    env={"PLUGIN": "tox"},
+                    env={"TOX_TESTENV_PASSENV": "http_proxy https_proxy"},
                     stdout=ANY,
                     stderr=ANY,
                 ),
diff --git a/lpcraft/plugins/plugins.py b/lpcraft/plugins/plugins.py
index 7708e35..880816e 100644
--- a/lpcraft/plugins/plugins.py
+++ b/lpcraft/plugins/plugins.py
@@ -34,10 +34,10 @@ def lpcraft_execute_run(self) -> str:
 
     @hookimpl  # type: ignore
     def lpcraft_set_environment(self) -> dict[str, str | None]:
-        # XXX jugmac00 2021-12-17: this was added to raise coverage and is not
-        # necessary. Let's remove this once we have a plugin which actually
-        # needs to set environment variables.
-        return {"PLUGIN": "tox"}
+        # Work around https://github.com/tox-dev/tox/issues/2372: without
+        # this, tox won't pass through the lower-case proxy environment
+        # variables set by launchpad-buildd.
+        return {"TOX_TESTENV_PASSENV": "http_proxy https_proxy"}
 
 
 @register(name="pyproject-build")