diff --git a/param/parameterized.py b/param/parameterized.py
index e43758d3d..3d49f9fad 100644
--- a/param/parameterized.py
+++ b/param/parameterized.py
@@ -426,6 +426,9 @@ def _f(self, obj, val):
             params = obj._param__private.params
             instance_param = None if params is None else params.get(self.name)
 
+            if (params is not None and instance_param is None):
+                instance_param = _instantiated_parameter(obj, self)
+
             if instance_param is not None and self is not instance_param:
                 instance_param.__set__(obj, val)
                 return
@@ -1404,7 +1407,7 @@ def __set__(self, obj, val):
                 warnings.warn(
                     'Number.set_hook has been deprecated.',
                     category=_ParamDeprecationWarning,
-                    stacklevel=5,
+                    stacklevel=6,
                 )
 
         self._validate(val)
diff --git a/tests/testselector.py b/tests/testselector.py
index 84ffffe42..1c4dc9d62 100644
--- a/tests/testselector.py
+++ b/tests/testselector.py
@@ -459,5 +459,4 @@ class B(A):
         b.p = 3
 
         assert A.param.p.objects == [1, 2]
-        assert B.param.p.objects == [1, 2, 3]
         assert b.param.p.objects == [1, 2, 3]