1 files changed, 4 insertions, 1 deletions

diff --git a/src/mailman/testing/layers.py b/src/mailman/testing/layers.py
index 4a9841fc2..38aa3907f 100644
--- a/src/mailman/testing/layers.py
+++ b/src/mailman/testing/layers.py
@@ -48,6 +48,7 @@ import tempfile
 from lazr.config import as_boolean
 from pkg_resources import resource_string
 from textwrap import dedent
+from zope import event
 from zope.component import getUtility
 
 from mailman.config import config
@@ -98,7 +99,9 @@ class ConfigLayer(MockAndMonkeyLayer):
         # Set up the basic configuration stuff.  Turn off path creation until
         # we've pushed the testing config.
         config.create_paths = False
-        initialize.initialize_1(INHIBIT_CONFIG_FILE)
+        if not event.subscribers:
+            # Only if not yet initialized by another layer.
+            initialize.initialize_1(INHIBIT_CONFIG_FILE)
         assert cls.var_dir is None, 'Layer already set up'
         # Calculate a temporary VAR_DIR directory so that run-time artifacts
         # of the tests won't tread on the installation's data.  This also