diff --git a/proxy_tests/proxy/shared/fast_add_peer/fp.rs b/proxy_tests/proxy/shared/fast_add_peer/fp.rs
index 5c5dbf5d240..b22805dfaa9 100644
--- a/proxy_tests/proxy/shared/fast_add_peer/fp.rs
+++ b/proxy_tests/proxy/shared/fast_add_peer/fp.rs
@@ -986,7 +986,7 @@ fn test_msgsnapshot_before_msgappend() {
         .unwrap();
 
     let mut t = 0;
-    while true {
+    loop {
         let mut buf = Vec::<raft::eraftpb::Entry>::new();
         cluster
             .get_engines(1)
diff --git a/proxy_tests/proxy/shared/replica_read.rs b/proxy_tests/proxy/shared/replica_read.rs
index d87a6ab87d2..438410d3a7b 100644
--- a/proxy_tests/proxy/shared/replica_read.rs
+++ b/proxy_tests/proxy/shared/replica_read.rs
@@ -210,6 +210,8 @@ fn test_read_index_normal() {
 
 /// If a read index request is received while region state is Applying,
 /// it could be handled correctly.
+/// NOTE even if we can handle Applying properly here, the read index will be
+/// reject in `resolveLocksAndWriteRegion` in TiFlash.
 #[test]
 fn test_read_index_applying() {
     // Initialize cluster
@@ -620,3 +622,102 @@ fn test_raft_message_can_advanve_max_ts() {
     cluster.shutdown();
     fail::remove("on_pre_write_apply_state")
 }
+
+#[test]
+fn test_read_index_diff_epoch() {
+    // Initialize cluster
+    let (mut cluster, pd_client) = new_mock_cluster(0, 2);
+    configure_for_lease_read(&mut cluster, Some(50), Some(10_000));
+    cluster.cfg.raft_store.raft_heartbeat_ticks = 1;
+    cluster.cfg.raft_store.raft_log_compact_sync_interval = ReadableDuration::millis(500);
+    pd_client.disable_default_operator();
+    disable_auto_gen_compact_log(&mut cluster);
+    // Otherwise will panic with `assert_eq!(apply_state, last_applied_state)`.
+    fail::cfg("on_pre_write_apply_state", "return(true)").unwrap();
+    // Set region and peers
+    let r1 = cluster.run_conf_change();
+    let p1 = new_peer(1, 1);
+    let p2 = new_learner_peer(2, 2);
+
+    cluster.pd_client.must_add_peer(r1, p2.clone());
+    cluster.must_put(b"k0", b"v");
+
+    let region = cluster.get_region(b"k0");
+    assert_eq!(cluster.leader_of_region(region.get_id()).unwrap(), p1);
+
+    check_key(&cluster, b"k0", b"v", Some(true), None, Some(vec![1, 2]));
+
+    for i in 1..5 {
+        cluster.must_put(format!("k{}0", i).as_bytes(), b"v");
+    }
+
+    check_key(&cluster, b"k40", b"v", Some(true), None, Some(vec![1, 2]));
+
+    cluster.must_split(&region, b"k20");
+
+    cluster.must_put(b"k11", b"v");
+    cluster.must_put(b"k31", b"v");
+    check_key(&cluster, b"k11", b"v", Some(true), None, Some(vec![1, 2]));
+    check_key(&cluster, b"k31", b"v", Some(true), None, Some(vec![1, 2]));
+
+    let waker = Waker::new();
+
+    let new_region = cluster.get_region(b"31");
+    let new_region_peer = new_region
+        .get_peers()
+        .iter()
+        .filter(|x| x.get_store_id() == 2)
+        .last()
+        .unwrap();
+
+    for (id, peer, f) in &[(2, p2, true), (2, new_region_peer.clone(), true)] {
+        iter_ffi_helpers(
+            &cluster,
+            Some(vec![*id]),
+            &mut |_, ffi_helper: &mut FFIHelperSet| {
+                assert_eq!(
+                    general_get_region_local_state(
+                        &ffi_helper.engine_store_server.engines.as_ref().unwrap().kv,
+                        r1
+                    )
+                    .unwrap()
+                    .get_state(),
+                    PeerState::Normal
+                );
+                let mut request = kvproto::kvrpcpb::ReadIndexRequest::default();
+
+                {
+                    let context = request.mut_context();
+                    context.set_region_id(region.get_id());
+                    context.set_peer(peer.clone());
+                    context.set_region_epoch(region.get_region_epoch().clone());
+                    request.set_start_ts(666);
+
+                    let mut range = kvproto::kvrpcpb::KeyRange::default();
+                    range.set_start_key(region.get_start_key().to_vec());
+                    range.set_end_key(region.get_end_key().to_vec());
+                    request.mut_ranges().push(range);
+
+                    debug!("make read index request {:?}", &request);
+                }
+                let w = if *f { Some(&waker) } else { None };
+                let resp = blocked_read_index(&request, &*ffi_helper.proxy_helper, w).unwrap();
+                assert_eq!(resp.get_read_index(), 0);
+                debug!("resp detail {:?}", resp);
+                // Epoch Not Match error
+                assert!(resp.has_region_error());
+            },
+        );
+    }
+
+    drop(waker);
+
+    {
+        assert!(!GC_MONITOR.is_empty());
+        assert!(GC_MONITOR.valid_clean());
+    }
+
+    cluster.shutdown();
+    fail::remove("on_pre_write_apply_state");
+    fail::remove("region_apply_snap");
+}