diff --git a/src/build/util.py b/src/build/util.py
index d7dc43b6..bbdfc758 100644
--- a/src/build/util.py
+++ b/src/build/util.py
@@ -2,6 +2,7 @@
 
 from __future__ import annotations
 
+import os
 import pathlib
 import tempfile
 
@@ -21,7 +22,7 @@ def _project_wheel_metadata(builder: ProjectBuilder) -> importlib.metadata.Packa
 
 def project_wheel_metadata(
     source_dir: StrPath,
-    isolated: bool = True,
+    isolated: bool = os.environ.get('BUILD_ENVIRONMENT', 'isolated') == 'isolated',
     *,
     runner: SubprocessRunner = pyproject_hooks.quiet_subprocess_runner,
 ) -> importlib.metadata.PackageMetadata:
@@ -34,7 +35,9 @@ def project_wheel_metadata(
     :param source_dir: Project source directory
     :param isolated: Whether or not to run invoke the backend in the current
                      environment or to create an isolated one and invoke it
-                     there.
+                     there. Defaults to True (isolated), but with
+                     ``BUILD_ENVIRONMENT=current`` set, the default
+                     is False.
     :param runner: An alternative runner for backend subprocesses
     """
 
diff --git a/tests/test_util.py b/tests/test_util.py
index 0ab81b84..1ab06c80 100644
--- a/tests/test_util.py
+++ b/tests/test_util.py
@@ -1,6 +1,8 @@
 # SPDX-License-Identifier: MIT
 
 import importlib.util
+import sys
+import subprocess
 
 import pytest
 
@@ -47,3 +49,11 @@ def test_with_get_requires(package_test_metadata):
     assert str(metadata['version']) == '1.0.0'
     assert metadata['summary'] == 'hello!'
     assert isinstance(metadata.json, dict)
+
+
+def test_current_environment_default():
+    check_script = "import build.util, inspect; print(inspect.signature(build.util.project_wheel_metadata).parameters['isolated'].default)"
+    cmd = [sys.executable, '-c', check_script]
+    env = {'BUILD_ENVIRONMENT': 'current'}
+    res = subprocess.check_output(cmd, env=env, text=True, encoding='utf-8')
+    assert res.strip() == 'False'