diff --git a/omegaconf/listconfig.py b/omegaconf/listconfig.py
index f98e8366f..f2b7b9ad7 100644
--- a/omegaconf/listconfig.py
+++ b/omegaconf/listconfig.py
@@ -98,19 +98,23 @@ def _validate_set(self, key: Any, value: Any) -> None:
                         "$FULL_KEY is not optional and cannot be assigned None"
                     )
 
-        is_optional, target_type = _resolve_optional(self._metadata.element_type)
-        value_type = OmegaConf.get_type(value)
-
-        if (value_type is None and not is_optional) or (
-            is_structured_config(target_type)
-            and value_type is not None
-            and not issubclass(value_type, target_type)
-        ):
-            msg = (
-                f"Invalid type assigned: {type_str(value_type)} is not a "
-                f"subclass of {type_str(target_type)}. value: {value}"
-            )
-            raise ValidationError(msg)
+        vk = get_value_kind(value)
+        if vk == ValueKind.MANDATORY_MISSING:
+            return
+        else:
+            is_optional, target_type = _resolve_optional(self._metadata.element_type)
+            value_type = OmegaConf.get_type(value)
+
+            if (value_type is None and not is_optional) or (
+                is_structured_config(target_type)
+                and value_type is not None
+                and not issubclass(value_type, target_type)
+            ):
+                msg = (
+                    f"Invalid type assigned: {type_str(value_type)} is not a "
+                    f"subclass of {type_str(target_type)}. value: {value}"
+                )
+                raise ValidationError(msg)
 
     def __deepcopy__(self, memo: Dict[int, Any]) -> "ListConfig":
         res = ListConfig(None)
diff --git a/tests/structured_conf/data/attr_classes.py b/tests/structured_conf/data/attr_classes.py
index ccb8b0811..a995a7e96 100644
--- a/tests/structured_conf/data/attr_classes.py
+++ b/tests/structured_conf/data/attr_classes.py
@@ -406,11 +406,21 @@ class DictOfObjects:
     users: Dict[str, User] = {"joe": User(name="Joe", age=18)}
 
 
+@attr.s(auto_attribs=True)
+class DictOfObjectsMissing:
+    users: Dict[str, User] = {"moe": MISSING}
+
+
 @attr.s(auto_attribs=True)
 class ListOfObjects:
     users: List[User] = [User(name="Joe", age=18)]
 
 
+@attr.s(auto_attribs=True)
+class ListOfObjectsMissing:
+    users: List[User] = [MISSING]
+
+
 class DictSubclass:
     @attr.s(auto_attribs=True)
     class Str2Str(Dict[str, str]):
diff --git a/tests/structured_conf/data/dataclasses.py b/tests/structured_conf/data/dataclasses.py
index 146dd4814..a59030171 100644
--- a/tests/structured_conf/data/dataclasses.py
+++ b/tests/structured_conf/data/dataclasses.py
@@ -427,11 +427,21 @@ class DictOfObjects:
     )
 
 
+@dataclass
+class DictOfObjectsMissing:
+    users: Dict[str, User] = field(default_factory=lambda: {"moe": MISSING})
+
+
 @dataclass
 class ListOfObjects:
     users: List[User] = field(default_factory=lambda: [User(name="Joe", age=18)])
 
 
+@dataclass
+class ListOfObjectsMissing:
+    users: List[User] = field(default_factory=lambda: [MISSING])
+
+
 class DictSubclass:
     @dataclass
     class Str2Str(Dict[str, str]):
diff --git a/tests/structured_conf/test_structured_config.py b/tests/structured_conf/test_structured_config.py
index 2cabdff3f..51bb9f37a 100644
--- a/tests/structured_conf/test_structured_config.py
+++ b/tests/structured_conf/test_structured_config.py
@@ -746,6 +746,20 @@ def test_dict_of_objects(self, module: Any) -> None:
         with raises(ValidationError):
             dct.fail = "fail"
 
+    def test_dict_of_objects_missing(self, module: Any) -> None:
+        conf = OmegaConf.structured(module.DictOfObjectsMissing)
+        dct = conf.users
+
+        assert OmegaConf.is_missing(dct, "moe")
+
+        dct.miss = MISSING
+        assert OmegaConf.is_missing(dct, "miss")
+
+    def test_assign_dict_of_objects(self, module: Any) -> None:
+        conf = OmegaConf.structured(module.DictOfObjects)
+        conf.users = {"poe": module.User(name="Poe", age=8), "miss": MISSING}
+        assert conf.users == {"poe": {"name": "Poe", "age": 8}, "miss": "???"}
+
     def test_list_of_objects(self, module: Any) -> None:
         conf = OmegaConf.structured(module.ListOfObjects)
         assert conf.users[0].age == 18
@@ -758,6 +772,19 @@ def test_list_of_objects(self, module: Any) -> None:
         with raises(ValidationError):
             conf.users.append("fail")
 
+    def test_list_of_objects_missing(self, module: Any) -> None:
+        conf = OmegaConf.structured(module.ListOfObjectsMissing)
+
+        assert OmegaConf.is_missing(conf.users, 0)
+
+        conf.users.append(MISSING)
+        assert OmegaConf.is_missing(conf.users, 1)
+
+    def test_assign_list_of_objects(self, module: Any) -> None:
+        conf = OmegaConf.structured(module.ListOfObjects)
+        conf.users = [module.User(name="Poe", age=8), MISSING]
+        assert conf.users == [{"name": "Poe", "age": 8}, "???"]
+
     def test_promote_api(self, module: Any) -> None:
         conf = OmegaConf.create(module.AnyTypeConfig)
         conf._promote(None)