diff --git a/src/core/xrootiface.py b/src/core/xrootiface.py
index e9fbf3ba..07b4e984 100644
--- a/src/core/xrootiface.py
+++ b/src/core/xrootiface.py
@@ -265,32 +265,32 @@ def rmxattr(endpoint, filepath, userid, key):
     _xrootcmd(endpoint, 'attr', 'rm', userid, 'mgm.attr.key=user.' + key + '&mgm.path=' + _getfilepath(filepath, encodeamp=True))
 
 
-def setlock(endpoint, filepath, userid, value):
+def setlock(endpoint, filepath, _userid, value):
     '''Set a lock as an xattr with the special option "c" (create-if-not-exists) on behalf of the given userid'''
     try:
         log.debug('msg="Invoked setlock" filepath="%s"' % filepath)
-        setxattr(endpoint, filepath, userid, LOCKKEY, str(value) + '&mgm.option=c')
+        setxattr(endpoint, filepath, '0:0', LOCKKEY, str(value) + '&mgm.option=c')
     except IOError as e:
         if EXCL_XATTR_MSG in str(e):
             raise IOError('File exists and islock flag requested')
 
 
-def getlock(endpoint, filepath, userid):
+def getlock(endpoint, filepath, _userid):
     '''Get the lock metadata as an xattr on behalf of the given userid'''
     log.debug('msg="Invoked getlock" filepath="%s"' % filepath)
-    return getxattr(endpoint, filepath, userid, LOCKKEY)
+    return getxattr(endpoint, filepath, '0:0', LOCKKEY)
 
 
-def refreshlock(endpoint, filepath, userid, value):
+def refreshlock(endpoint, filepath, _userid, value):
     '''Refresh the lock value as an xattr on behalf of the given userid'''
     log.debug('msg="Invoked refreshlock" filepath="%s"' % filepath)
-    if getxattr(endpoint, filepath, userid, LOCKKEY):
-        setxattr(endpoint, filepath, userid, LOCKKEY, value)   # non-atomic, but the lock was already held
+    if getxattr(endpoint, filepath, '0:0', LOCKKEY):
+        setxattr(endpoint, filepath, '0:0', LOCKKEY, value)   # non-atomic, but the lock was already held
     else:
         raise IOError('File was not locked')
 
 
-def unlock(endpoint, filepath, userid):
+def unlock(endpoint, filepath, _userid):
     '''Remove a lock as an xattr on behalf of the given userid'''
     log.debug('msg="Invoked unlock" filepath="%s"' % filepath)
     rmxattr(endpoint, filepath, userid, LOCKKEY)