diff --git a/crates/wip-client/src/lib.rs b/crates/wip-client/src/lib.rs
index aa3d166..2465727 100644
--- a/crates/wip-client/src/lib.rs
+++ b/crates/wip-client/src/lib.rs
@@ -1707,6 +1707,29 @@ fn object_ownership_revision(state: &Session, key: u64) -> Option<RequestId> {
         .max()
 }
 
+fn validate_object_consistency(state: &Session, object: &Object) -> Result<(), ClientError> {
+    let Some(reference) = &object.r#ref else {
+        return Ok(());
+    };
+    let Some(existing) = state
+        .refs
+        .get(reference)
+        .and_then(|key| state.objects.get(key))
+    else {
+        return Ok(());
+    };
+    if existing.object.validator.is_some()
+        && existing.object.validator == object.validator
+        && existing.object != *object
+    {
+        return Err(ClientError::new(
+            ClientErrorKind::InvalidResponse,
+            "object representation changed for the same ref and validator",
+        ));
+    }
+    Ok(())
+}
+
 fn insert_object(
     state: &mut Session,
     path: &str,
@@ -1714,6 +1737,7 @@ fn insert_object(
     maximum: usize,
     revision: RequestId,
 ) -> Result<u64, ClientError> {
+    validate_object_consistency(state, &object)?;
     ensure_entry_slot(state, path, maximum)?;
     let existing_path_entry = state.entries.get(path).cloned();
     let existing_path_key = existing_path_entry
@@ -1731,16 +1755,6 @@ fn insert_object(
     });
     let key = if let Some(reference) = &object.r#ref {
         if let Some(key) = state.refs.get(reference).copied() {
-            if let Some(existing) = state.objects.get(&key)
-                && existing.object.validator.is_some()
-                && existing.object.validator == object.validator
-                && existing.object != object
-            {
-                return Err(ClientError::new(
-                    ClientErrorKind::InvalidResponse,
-                    "object representation changed for the same ref and validator",
-                ));
-            }
             key
         } else {
             make_object_slot(state, maximum, replaceable_key)?
@@ -2017,6 +2031,7 @@ fn apply_tree(
     }
 
     for (path, object, _) in &nodes {
+        validate_object_consistency(state, object)?;
         let newer_owner = state
             .entries
             .get(path)
diff --git a/crates/wip-client/tests/runtime.rs b/crates/wip-client/tests/runtime.rs
index 3b539b1..d2c877f 100644
--- a/crates/wip-client/tests/runtime.rs
+++ b/crates/wip-client/tests/runtime.rs
@@ -327,6 +327,53 @@ fn normalized_aliases_preserve_newer_request_ownership() {
         client.object(&session, "/b/shared").unwrap().validator,
         Some(b"newest".to_vec())
     );
+
+    observe_object(
+        &mut client,
+        &session,
+        "/child",
+        object("child", Some("child-ref"), b"stable"),
+    );
+    let older_tree = client.prepare_tree(&session, "/", 1, 4).unwrap();
+    let newer_child = client.prepare_fetch(&session, "/child").unwrap();
+    client
+        .complete(
+            newer_child.id,
+            fetch_response("/child", &object("child", Some("child-ref"), b"stable")),
+        )
+        .unwrap();
+    let mut contradictory = object("child", Some("child-ref"), b"stable");
+    contradictory.description = Some("same-path contradiction".into());
+    let root_request = FetchTreeRequest {
+        path: "/".into(),
+        depth: 1,
+        limit: 4,
+    };
+    let error = client
+        .complete(
+            older_tree.id,
+            encode_fetch_tree_response(
+                &root_request,
+                &FetchTreeResponse {
+                    root: ObjectTreeNode {
+                        object: object("", None, b"root"),
+                        children: vec![ObjectTreeNode {
+                            object: contradictory,
+                            children: vec![],
+                        }],
+                    },
+                    truncated: false,
+                },
+                wire_limits(),
+            )
+            .unwrap(),
+        )
+        .unwrap_err();
+    assert_eq!(error.kind, ClientErrorKind::InvalidResponse);
+    assert_eq!(
+        client.object(&session, "/child").unwrap().state,
+        ObservationState::Fresh
+    );
 }
 
 #[test]