diff --git a/setuptools/tests/fixtures.py b/setuptools/tests/fixtures.py
index 524c6cbd2..90d82e7c7 100644
--- a/setuptools/tests/fixtures.py
+++ b/setuptools/tests/fixtures.py
@@ -82,6 +82,7 @@ def setuptools_sdist(tmp_path_factory, request):
                 "-m",
                 "build",
                 "--sdist",
+                "--no-isolation",
                 "--outdir",
                 str(tmp),
                 str(request.config.rootdir),
@@ -108,6 +109,7 @@ def setuptools_wheel(tmp_path_factory, request):
                 "-m",
                 "build",
                 "--wheel",
+                "--no-isolation",
                 "--outdir",
                 str(tmp),
                 str(request.config.rootdir),