diff --git a/setup/test.py b/setup/test.py
index 6855681be6..6cdf028785 100644
--- a/setup/test.py
+++ b/setup/test.py
@@ -46,6 +46,8 @@ 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/src/calibre/srv/tests/auth.py b/src/calibre/srv/tests/auth.py
index 94fd56b8e4..e277a34deb 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)
+                    p = subprocess.Popen(cmd, stdout=subprocess.PIPE, stderr=subprocess.DEVNULL, env=getattr(os, 'non_calibre_subprocess_env', os.environ))
                     x = p.stdout.read()
                     p.wait()
                     self.ae(x, data)