diff --git a/setup/test.py b/setup/test.py
index 6cdf028785..6855681be6 100644
--- a/setup/test.py
+++ b/setup/test.py
@@ -46,8 +46,6 @@ class Test(Command):
             sys.libxslt_dylib = ctypes.CDLL(os.path.join(os.environ['SW'], 'lib', 'libxslt.dylib'))
             sys.libexslt_dylib = ctypes.CDLL(os.path.join(os.environ['SW'], 'lib', 'libexslt.dylib'))
             print(sys.libxml2_dylib, sys.libxslt_dylib, sys.libexslt_dylib, file=sys.stderr, flush=True)
-            os.non_calibre_subprocess_env = e = os.environ
-            del e['DYLD_LIBRARY_PATH']
         from calibre.utils.run_tests import (
             filter_tests_by_name, remove_tests_by_name, run_cli, find_tests
         )
diff --git a/setup/unix-ci.py b/setup/unix-ci.py
index 733df81c70..5b05c9aebe 100644
--- a/setup/unix-ci.py
+++ b/setup/unix-ci.py
@@ -161,7 +161,8 @@ username = api
         if ismacos:
             os.environ['SSL_CERT_FILE'] = os.path.abspath(
                 'resources/mozilla-ca-certs.pem')
-            os.environ['DYLD_LIBRARY_PATH'] = os.path.join(SW, 'lib')  # needed to ensure correct libxml2.dylib is loaded
+            # needed to ensure correct libxml2 is loaded
+            os.environ['DYLD_INSERT_LIBRARIES'] = ':'.join(os.path.join(SW, 'lib', x) for x in 'libxml2.dylib libxslt.dylib libexslt.dylib'.split())
 
         install_env()
         run_python('setup.py test')
diff --git a/src/calibre/srv/tests/auth.py b/src/calibre/srv/tests/auth.py
index e277a34deb..94fd56b8e4 100644
--- a/src/calibre/srv/tests/auth.py
+++ b/src/calibre/srv/tests/auth.py
@@ -233,7 +233,7 @@ class TestAuth(BaseTest):
             if curl:
                 def docurl(data, *args):
                     cmd = [curl] + list(args) + ['http://localhost:%d/closed' % server.address[1]]
-                    p = subprocess.Popen(cmd, stdout=subprocess.PIPE, stderr=subprocess.DEVNULL, env=getattr(os, 'non_calibre_subprocess_env', os.environ))
+                    p = subprocess.Popen(cmd, stdout=subprocess.PIPE, stderr=subprocess.DEVNULL)
                     x = p.stdout.read()
                     p.wait()
                     self.ae(x, data)