diff --git a/pyproject.toml b/pyproject.toml
index e7e576b0..c67ea911 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -8,7 +8,7 @@ build-backend = "setuptools.build_meta"
 [project]
 name = "ops-scenario"
 
-version = "4.0.1"
+version = "4.0.2"
 
 authors = [
     { name = "Pietro Pasotti", email = "pietro.pasotti@canonical.com" }
diff --git a/scenario/state.py b/scenario/state.py
index 024721d8..42ee70dd 100644
--- a/scenario/state.py
+++ b/scenario/state.py
@@ -80,9 +80,11 @@ class StateValidationError(RuntimeError):
 @dataclasses.dataclass(frozen=True)
 class _DCBase:
     def replace(self, *args, **kwargs):
-        return dataclasses.replace(self, *args, **kwargs)
+        """Produce a deep copy of this class, with some arguments replaced with new ones."""
+        return dataclasses.replace(self.copy(), *args, **kwargs)
 
     def copy(self) -> "Self":
+        """Produce a deep copy of this object."""
         return copy.deepcopy(self)
 
 
diff --git a/tests/test_consistency_checker.py b/tests/test_consistency_checker.py
index c5000d44..a1bf26b4 100644
--- a/tests/test_consistency_checker.py
+++ b/tests/test_consistency_checker.py
@@ -287,7 +287,7 @@ def test_relation_without_endpoint():
 
     assert_consistent(
         State(
-            relations=[Relation("foo", relation_id=1), Relation("bar", relation_id=1)]
+            relations=[Relation("foo", relation_id=1), Relation("bar", relation_id=2)]
         ),
         Event("start"),
         _CharmSpec(
diff --git a/tests/test_dcbase.py b/tests/test_dcbase.py
new file mode 100644
index 00000000..fd5ff872
--- /dev/null
+++ b/tests/test_dcbase.py
@@ -0,0 +1,41 @@
+import dataclasses
+from typing import Dict, List
+
+from scenario.state import _DCBase
+
+
+@dataclasses.dataclass(frozen=True)
+class Foo(_DCBase):
+    a: int
+    b: List[int]
+    c: Dict[int, List[int]]
+
+
+def test_base_case():
+    l = [1, 2]
+    l1 = [1, 2, 3]
+    d = {1: l1}
+    f = Foo(1, l, d)
+    g = f.replace(a=2)
+
+    assert g.a == 2
+    assert g.b == l
+    assert g.c == d
+    assert g.c[1] == l1
+
+
+def test_dedup_on_replace():
+    l = [1, 2]
+    l1 = [1, 2, 3]
+    d = {1: l1}
+    f = Foo(1, l, d)
+    g = f.replace(a=2)
+
+    l.append(3)
+    l1.append(4)
+    d[2] = "foobar"
+
+    assert g.a == 2
+    assert g.b == [1, 2]
+    assert g.c == {1: [1, 2, 3]}
+    assert g.c[1] == [1, 2, 3]