diff --git a/src/west/manifest.py b/src/west/manifest.py
index 7d716ec..f73e5d6 100644
--- a/src/west/manifest.py
+++ b/src/west/manifest.py
@@ -1361,7 +1361,7 @@ class Manifest:
         self._posixpath: Optional[str] = None
         self._repo_posixpath: Optional[str] = None
         # This backs the userdata property
-        self._userdata: Optional[Any] = None
+        self.userdata: Any = None
         # Load context needed for import resolution. Do top-level
         # argument validation and storage if self._top_level is True,
         # but otherwise just get self._ctx from the caller.
@@ -1803,7 +1803,7 @@ class Manifest:
             mp = ManifestProject(
                 path=self._config_path if self.topdir else self.yaml_path,
                 west_commands=self._ctx.manifest_west_commands,
-                topdir=self.topdir, userdata=self._userdata)
+                topdir=self.topdir, userdata=self.userdata)
 
             # Save the resulting projects and initialize lookup tables
             # that rely on the ManifestProject existing.
@@ -1906,7 +1906,7 @@ class Manifest:
             _logger.debug('resolved self import')
 
         userdata = slf.get('userdata')
-        self._userdata = userdata
+        self.userdata = userdata
 
         # The current manifest data's west-comands comes first because
         # we treat imports from self as if they are defined "before"
diff --git a/tests/test_manifest.py b/tests/test_manifest.py
index 3b3c27b..cd8d0f5 100644
--- a/tests/test_manifest.py
+++ b/tests/test_manifest.py
@@ -589,12 +589,34 @@ def test_self_userdata(tmpdir):
     ''')
     foo, bar = m.get_projects(['manifest', 'bar'])
 
+    assert m.userdata == {'key': 'value'}
     assert foo.userdata == {'key': 'value'}
     assert bar.userdata is None
     assert 'userdata' in foo.as_dict()
     assert 'userdata' not in bar.as_dict()
 
 
+def test_self_missing_userdata(tmpdir):
+    m = M('''
+    defaults:
+      remote: r
+    remotes:
+      - name: r
+        url-base: base
+    projects:
+    - name: bar
+    self:
+      path: foo
+    ''')
+    foo, bar = m.get_projects(['manifest', 'bar'])
+
+    assert m.userdata is None
+    assert foo.userdata is None
+    assert bar.userdata is None
+    assert 'userdata' not in foo.as_dict()
+    assert 'userdata' not in bar.as_dict()
+
+
 def test_no_projects():
     # An empty projects list is allowed.