diff --git a/swh/model/model.py b/swh/model/model.py
--- a/swh/model/model.py
+++ b/swh/model/model.py
@@ -91,10 +91,18 @@
 
     # Non-generic type, check it directly
     if origin is None:
-        return type(value) == type_
+        # This is functionally equivalent to using just this:
+        #   return isinstance(value, type)
+        # but using type equality before isinstance allows very quick checks
+        # when the exact class is used (which is the overwhelming majority of cases)
+        # while still allowing subclasses to be used.
+        return type(value) == type_ or isinstance(value, type_)
 
     # Check the type of the value itself
-    if origin is not Union and type(value) != origin:
+    #
+    # For the same reason as above, this condition is functionally equivalent to:
+    #   if origin is not Union and not isinstance(value, origin):
+    if origin is not Union and type(value) != origin and not isinstance(value, origin):
         return False
 
     # Then, if it's a container, check its items.
diff --git a/swh/model/tests/test_model.py b/swh/model/tests/test_model.py
--- a/swh/model/tests/test_model.py
+++ b/swh/model/tests/test_model.py
@@ -3,6 +3,7 @@
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
+import collections
 import copy
 import datetime
 from typing import Any, List, Optional, Tuple, Union
@@ -74,6 +75,23 @@
     assert obj_as_dict == type(obj).from_dict(obj_as_dict).to_dict()
 
 
+@attr.s
+class Cls1:
+    pass
+
+
+@attr.s
+class Cls2(Cls1):
+    pass
+
+
+_custom_namedtuple = collections.namedtuple("_custom_namedtuple", "a b")
+
+
+class _custom_tuple(tuple):
+    pass
+
+
 # List of (type, valid_values, invalid_values)
 _TYPE_VALIDATOR_PARAMETERS: List[Tuple[Any, List[Any], List[Any]]] = [
     # base types:
@@ -84,8 +102,8 @@
     ),
     (
         int,
-        [-1, 0, 1, 42, 1000],
-        [True, False, None, "123", 0.0, (), ImmutableDict(), DentryPerms.directory],
+        [-1, 0, 1, 42, 1000, DentryPerms.directory, True, False],
+        [None, "123", 0.0, (), ImmutableDict()],
     ),
     (
         float,
@@ -101,8 +119,8 @@
     # unions:
     (
         Optional[int],
-        [None, -1, 0, 1, 42, 1000],
-        ["123", 0.0, (), ImmutableDict(), DentryPerms.directory],
+        [None, -1, 0, 1, 42, 1000, DentryPerms.directory],
+        ["123", 0.0, (), ImmutableDict()],
     ),
     (
         Optional[bytes],
@@ -122,12 +140,19 @@
     # tuples
     (
         Tuple[str, str],
-        [("foo", "bar"), ("", "")],
+        [("foo", "bar"), ("", ""), _custom_namedtuple("", ""), _custom_tuple(("", ""))],
         [("foo",), ("foo", "bar", "baz"), ("foo", 42), (42, "foo")],
     ),
     (
         Tuple[str, ...],
-        [("foo",), ("foo", "bar"), ("", ""), ("foo", "bar", "baz")],
+        [
+            ("foo",),
+            ("foo", "bar"),
+            ("", ""),
+            ("foo", "bar", "baz"),
+            _custom_namedtuple("", ""),
+            _custom_tuple(("", "")),
+        ],
         [("foo", 42), (42, "foo")],
     ),
     # composite generic:
@@ -163,6 +188,7 @@
         [ImmutableDict({"foo": "bar"}), ImmutableDict({42: 123})],
     ),
     # Any:
+    (object, [-1, 0, 1, 42, 1000, None, "123", 0.0, (), ImmutableDict()], [],),
     (Any, [-1, 0, 1, 42, 1000, None, "123", 0.0, (), ImmutableDict()], [],),
     (
         ImmutableDict[Any, int],
@@ -187,9 +213,10 @@
     # attr objects:
     (
         Timestamp,
-        [Timestamp(seconds=123, microseconds=0)],
+        [Timestamp(seconds=123, microseconds=0),],
         [None, "2021-09-28T11:27:59", 123],
     ),
+    (Cls1, [Cls1(), Cls2()], [None, b"abcd"],),
     # enums:
     (
         TargetType,
@@ -202,7 +229,7 @@
 @pytest.mark.parametrize(
     "type_,value",
     [
-        (type_, value)
+        pytest.param(type_, value, id=f"type={type_}, value={value}")
         for (type_, values, _) in _TYPE_VALIDATOR_PARAMETERS
         for value in values
     ],
@@ -214,7 +241,7 @@
 @pytest.mark.parametrize(
     "type_,value",
     [
-        (type_, value)
+        pytest.param(type_, value, id=f"type={type_}, value={value}")
         for (type_, _, values) in _TYPE_VALIDATOR_PARAMETERS
         for value in values
     ],