diff --git a/dkimpy_milter/__init__.py b/dkimpy_milter/__init__.py
index bcdf2a7..3f9eef9 100644
--- a/dkimpy_milter/__init__.py
+++ b/dkimpy_milter/__init__.py
@@ -354,7 +354,9 @@ def main():
     Milter.set_flags(Milter.CHGHDRS + Milter.ADDHDRS)
     miltername = 'dkimpy-filter'
     socketname = milterconfig.get('Socket')
-    own_socketfile(milterconfig)
+    if socketname is None:
+        socketname = 'local:/var/run/dkimpy-milter/dkimpy-milter.sock'
+    own_socketfile(milterconfig, socketname)
     drop_privileges(milterconfig)
     sys.stdout.flush()
     Milter.runmilter(miltername, socketname, 240)
diff --git a/dkimpy_milter/config.py b/dkimpy_milter/config.py
index bf6551a..c59ce55 100644
--- a/dkimpy_milter/config.py
+++ b/dkimpy_milter/config.py
@@ -39,7 +39,7 @@ defaultConfigData = {
     'SyslogFacility': 'mail',
     'UMask': 0o07,
     'Mode': 'sv',
-    'Socket': 'local:/var/run/dkimpy-milter/dkimpy-milter.sock',
+    'Socket': None,
     'PidFile': '/var/run/dkimpy-milter/dkimpy-milter.pid',
     'UserID': 'dkimpy-milter',
     'Canonicalization': 'relaxed/simple',
diff --git a/dkimpy_milter/util.py b/dkimpy_milter/util.py
index 17857d6..1d5788d 100644
--- a/dkimpy_milter/util.py
+++ b/dkimpy_milter/util.py
@@ -146,12 +146,15 @@ def write_pid(milterconfig):
     return pid
 
 
-def own_socketfile(milterconfig):
+def own_socketfile(milterconfig, sockname=None):
     """If socket is Unix socket, chown to UserID before dropping privileges"""
     import os
     user, group = user_group(milterconfig.get('UserID'))
     offset = None
-    sockname = milterconfig.get('Socket')
+    if sockname is None:
+        sockname = milterconfig.get('Socket')
+    if sockname is None:
+        return
     if sockname[:1] == '/':
         offset = 0
     elif sockname[:6] == "local:":