diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 67d27aef..9057b346 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -55,7 +55,6 @@ repos:
     hooks:
       - id: mypy
         files: src
-        args: ["--enable-incomplete-feature=Unpack"]
         additional_dependencies:
           - pytest
 
diff --git a/src/galdynamix/utils/_collections.py b/src/galdynamix/utils/_collections.py
index a6c88cf0..2925abb4 100644
--- a/src/galdynamix/utils/_collections.py
+++ b/src/galdynamix/utils/_collections.py
@@ -4,11 +4,12 @@
 __all__ = ["ImmutableDict"]
 
 from collections.abc import ItemsView, Iterable, Iterator, KeysView, Mapping, ValuesView
-from typing import TypeVar
+from typing import Any, TypeVar
 
 from jax.tree_util import register_pytree_node_class
 
 V = TypeVar("V")
+T = TypeVar("T")
 
 
 @register_pytree_node_class
@@ -64,6 +65,15 @@ def items(self) -> ItemsView[str, V]:
     def __repr__(self) -> str:
         return f"{self.__class__.__name__}({self._data!r})"
 
+    def __or__(self, value: Any, /) -> "ImmutableDict[V]":
+        if not isinstance(value, Mapping):
+            return NotImplemented
+
+        return type(self)(self._data | dict(value))
+
+    def __ror__(self, value: Any) -> Any:
+        return value | self._data
+
     # === PyTree ===
 
     def tree_flatten(self) -> tuple[tuple[V, ...], tuple[str, ...]]:
diff --git a/tests/utils/test_collections.py b/tests/utils/test_collections.py
index 36a0ec3d..f2571767 100644
--- a/tests/utils/test_collections.py
+++ b/tests/utils/test_collections.py
@@ -1,3 +1,6 @@
+from collections import OrderedDict
+from types import MappingProxyType
+
 import pytest
 
 from galdynamix.utils import ImmutableDict
@@ -69,6 +72,20 @@ def test_repr(self):
         d = ImmutableDict(a=1, b=2)
         assert repr(d) == "ImmutableDict({'a': 1, 'b': 2})"
 
+    def test_or(self):
+        """Test `__or__`."""
+        d = ImmutableDict(a=1, b=2)
+        assert d | ImmutableDict(c=3) == ImmutableDict(a=1, b=2, c=3)
+        assert d | {"c": 3} == ImmutableDict(a=1, b=2, c=3)
+        assert d | OrderedDict([("c", 3)]) == ImmutableDict(a=1, b=2, c=3)
+        assert d | MappingProxyType({"c": 3}) == ImmutableDict(a=1, b=2, c=3)
+
+        # Reverse order
+        assert {"c": 3} | d == {"c": 3, "a": 1, "b": 2}
+        assert OrderedDict([("c", 3)]) | d == OrderedDict(
+            [("c", 3), ("a", 1), ("b", 2)]
+        )
+
     # === Test pytree methods ===
 
     def test_tree_flatten(self):