diff --git a/lisa/env.py b/lisa/env.py
index 27b0d3dc654b8724187887934113cd7debe087c0..1747d0f76e36ffc5527c4a3dc1e9484465ee6014 100644
--- a/lisa/env.py
+++ b/lisa/env.py
@@ -125,7 +125,6 @@ class TargetConf(MultiSrcConf, HideExekallID):
         KeyDesc('port', 'SSH or ADB server port', [int, None]),
         KeyDesc('device', 'ADB device. Takes precedence over "host"', [str, None]),
         KeyDesc('keyfile', 'SSH private key file', [str, None]),
-
         KeyDesc('workdir', 'Remote target workdir', [str]),
         KeyDesc('tools', 'List of tools to install on the target', [StrList]),
         LevelKeyDesc('ftrace', 'FTrace configuration', (
@@ -146,7 +145,7 @@ class TargetConf(MultiSrcConf, HideExekallID):
         ))
     ))
 
-    DEFAULT_CONF = {
+    DEFAULT_SRC = {
         'username': USERNAME_DEFAULT,
         'ftrace': {
             'buffsize': FTRACE_BUFSIZE_DEFAULT,
@@ -160,8 +159,6 @@ class TargetConf(MultiSrcConf, HideExekallID):
 
     def __init__(self, conf, src='user'):
         super().__init__(conf=conf, src=src)
-        # Give some preset in the the lowest prio source
-        self.add_src('default', self.DEFAULT_CONF, fallback=True)
 
     # We do not allow overriding source for this kind of configuration to keep
     # the YAML interface simple and dict-like
diff --git a/lisa/utils.py b/lisa/utils.py
index a796649235e7db8974245b3a5975eaf8a5f3d5c9..29645f280e9596f0ab290186e573672d328ca8c2 100644
--- a/lisa/utils.py
+++ b/lisa/utils.py
@@ -697,8 +697,13 @@ class MultiSrcConf(SerializableConfABC, Loggable, Mapping, metaclass=MultiSrcCon
         """
         pass
 
-    def __init__(self, conf=None, src='default'):
+    DEFAULT_SRC = {}
+    """
+    Source added automatically using :meth:`add_src` under the name 'default'
+    when instances are built.
+    """
 
+    def __init__(self, conf=None, src='conf'):
         self._nested_init(
             parent=None,
             structure=self.STRUCTURE,
@@ -707,6 +712,10 @@ class MultiSrcConf(SerializableConfABC, Loggable, Mapping, metaclass=MultiSrcCon
         if conf is not None:
             self.add_src(src, conf)
 
+        # Give some preset in the the lowest prio source
+        if self.DEFAULT_SRC:
+            self.add_src('default', self.DEFAULT_SRC, fallback=True)
+
     @classmethod
     def get_help(cls, *args, **kwargs):
         return cls.STRUCTURE.get_help(*args, **kwargs)