diff --git a/CHANGELOG.md b/CHANGELOG.md
index ec93530..0acdbb1 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,6 +9,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Changed
 
+- User-provided environment variables are now propagated to subprocesses such as `pip install`. ([#65](https://github.com/heroku/buildpacks-python/pull/65))
 - Updated pip from 23.1.2 to 23.2. ([#67](https://github.com/heroku/buildpacks-python/pull/67))
 - Updated setuptools from 67.8.0 to 68.0.0. ([#51](https://github.com/heroku/buildpacks-python/pull/51))
 
diff --git a/buildpack.toml b/buildpack.toml
index 961ebdd..e8ac309 100644
--- a/buildpack.toml
+++ b/buildpack.toml
@@ -7,7 +7,6 @@ name = "Python"
 homepage = "https://github.com/heroku/buildpacks-python"
 description = "Heroku's official Python Cloud Native Buildpack."
 keywords = ["python", "heroku"]
-clear-env = true
 
 [[buildpack.licenses]]
 type = "BSD-3-Clause"
diff --git a/src/layers/python.rs b/src/layers/python.rs
index 8b75d66..8656628 100644
--- a/src/layers/python.rs
+++ b/src/layers/python.rs
@@ -321,6 +321,8 @@ fn generate_layer_env(layer_path: &Path, python_version: &PythonVersion) -> Laye
         // However, the uWSGI package uses the wrong `sysconfig` APIs so tries to reference the old
         // compile location, unless we override that by setting `PYTHONHOME`:
         // https://github.com/unbit/uwsgi/issues/2525
+        // In addition, some legacy apps have `PYTHONHOME` set to an invalid value, so if we did not
+        // set it explicitly here, Python would fail to run both during the build and at runtime.
         .chainable_insert(
             Scope::All,
             ModificationBehavior::Override,
diff --git a/src/main.rs b/src/main.rs
index 6a2b637..b058417 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -66,10 +66,10 @@ impl Buildpack for PythonBuildpack {
         let packaging_tool_versions = PackagingToolVersions::default();
 
         // We inherit the current process's env vars, since we want `PATH` and `HOME` from the OS
-        // to be set, so that later commands can find tools like Git in the stack image. We exclude
-        // user-provided env vars (by setting `clear-env` to true in `buildpack.toml`) to prevent an
-        // app's env vars from breaking internal buildpack commands. Any buildpack steps that need
-        // user-provided env vars must explicitly retrieve them via `context.platform.env`.
+        // to be set (so that later commands can find tools like Git in the stack image), along
+        // with previous-buildpack or user-provided env vars (so that features like env vars in
+        // in requirements files work). We protect against broken user-provided env vars by
+        // making sure that buildpack env vars take precedence in layers envs and command usage.
         let mut command_env = Env::from_current();
 
         // Create the layer containing the Python runtime, and the packages `pip`, `setuptools` and `wheel`.
diff --git a/tests/fixtures/pip_editable_git_compiled/requirements.txt b/tests/fixtures/pip_editable_git_compiled/requirements.txt
index a6710b5..a9b27b0 100644
--- a/tests/fixtures/pip_editable_git_compiled/requirements.txt
+++ b/tests/fixtures/pip_editable_git_compiled/requirements.txt
@@ -4,5 +4,8 @@
 #
 # A C-based package is used instead of a pure Python package, in order to test that the
 # Python headers can be found in the `include/pythonX.Y/` directory of the Python layer.
+#
+# The URL to the package is specified via env var, to test that user-provided env vars
+# are propagated to pip for use by its env var interpolation feature.
 
--e git+https://github.com/pypa/wheel@0.40.0#egg=extension.dist&subdirectory=tests/testdata/extension.dist
+-e git+${WHEEL_PACKAGE_URL}@0.40.0#egg=extension.dist&subdirectory=tests/testdata/extension.dist
diff --git a/tests/integration/pip.rs b/tests/integration/pip.rs
index e7aa13c..0a14caf 100644
--- a/tests/integration/pip.rs
+++ b/tests/integration/pip.rs
@@ -156,6 +156,7 @@ fn pip_cache_invalidation_and_metadata_compatibility() {
 }
 
 // This tests that:
+//  - Requirements file env var interpolation works (ie: user-provided env vars have been propagated to pip).
 //  - Git from the stack image can be found (ie: the system PATH has been correctly propagated to pip).
 //  - The editable mode repository clone is saved into the dependencies layer not the app dir.
 //  - Compiling a source distribution package (as opposed to a pre-built wheel) works.
@@ -164,7 +165,8 @@ fn pip_cache_invalidation_and_metadata_compatibility() {
 #[ignore = "integration test"]
 fn pip_editable_git_compiled() {
     TestRunner::default().build(
-        BuildConfig::new(builder(), "tests/fixtures/pip_editable_git_compiled"),
+        BuildConfig::new(builder(), "tests/fixtures/pip_editable_git_compiled")
+            .env("WHEEL_PACKAGE_URL", "https://github.com/pypa/wheel"),
         |context| {
             assert_contains!(
                 context.pack_stdout,
diff --git a/tests/integration/python_version.rs b/tests/integration/python_version.rs
index dbc1e3e..cb872db 100644
--- a/tests/integration/python_version.rs
+++ b/tests/integration/python_version.rs
@@ -76,9 +76,17 @@ fn builds_with_python_version(fixture_path: &str, python_version: &str) {
     } = PackagingToolVersions::default();
 
     let mut config = BuildConfig::new(builder(), fixture_path);
-    // Checks that potentially broken user-provided env vars are not being passed unfiltered to
-    // subprocesses we launch (such as `pip install`), thanks to `clear-env` in `buildpack.toml`.
-    config.env("PYTHONHOME", "/invalid-path");
+    // Checks that potentially broken user-provided env vars don't take precedence over those
+    // set by this buildpack and break running Python. These are based on the env vars that
+    // used to be set by `bin/release` by very old versions of the classic Python buildpack:
+    // https://github.com/heroku/heroku-buildpack-python/blob/27abdfe7d7ad104dabceb45641415251e965671c/bin/release#L11-L18
+    config.envs([
+        ("LD_LIBRARY_PATH", "/invalid-path"),
+        ("LIBRARY_PATH", "/invalid-path"),
+        ("PATH", "/invalid-path"),
+        ("PYTHONHOME", "/invalid-path"),
+        ("PYTHONPATH", "/invalid-path"),
+    ]);
 
     TestRunner::default().build(config, |context| {
         assert_empty!(context.pack_stderr);