diff --git a/crates/loro-internal/src/handler.rs b/crates/loro-internal/src/handler.rs
index 3857ea51..02ade94a 100644
--- a/crates/loro-internal/src/handler.rs
+++ b/crates/loro-internal/src/handler.rs
@@ -284,6 +284,13 @@ impl TextHandler {
             return Ok(());
         }
 
+        if pos > self.len_event() {
+            return Err(LoroError::OutOfBound {
+                pos,
+                len: self.len_event(),
+            });
+        }
+
         let (entity_index, styles) = self
             .state
             .upgrade()
@@ -424,6 +431,11 @@ impl TextHandler {
             ));
         }
 
+        let len = self.len_event();
+        if end > len {
+            return Err(LoroError::OutOfBound { pos: end, len });
+        }
+
         let (entity_start, entity_end) = self
             .state
             .upgrade()
@@ -551,6 +563,13 @@ impl ListHandler {
     }
 
     pub fn insert(&self, txn: &mut Transaction, pos: usize, v: LoroValue) -> LoroResult<()> {
+        if pos > self.len() {
+            return Err(LoroError::OutOfBound {
+                pos,
+                len: self.len(),
+            });
+        }
+
         if let Some(container) = v.as_container() {
             self.insert_container(txn, pos, container.container_type())?;
             return Ok(());
@@ -631,6 +650,13 @@ impl ListHandler {
             return Ok(());
         }
 
+        if pos + len > self.len() {
+            return Err(LoroError::OutOfBound {
+                pos: pos + len,
+                len: self.len(),
+            });
+        }
+
         txn.apply_local_op(
             self.container_idx,
             crate::op::RawOpContent::List(ListOp::Delete(DeleteSpan {
diff --git a/crates/loro-internal/tests/test.rs b/crates/loro-internal/tests/test.rs
index b105ecf8..37b60be7 100644
--- a/crates/loro-internal/tests/test.rs
+++ b/crates/loro-internal/tests/test.rs
@@ -18,9 +18,26 @@ fn list() {
         .into_map()
         .unwrap();
     map.insert_("Hello", LoroValue::from("u")).unwrap();
+    let pos = map
+        .insert_container_("pos", ContainerType::Map)
+        .unwrap()
+        .into_map()
+        .unwrap();
+    pos.insert_("x", 0.into()).unwrap();
+    pos.insert_("y", 100.into()).unwrap();
+
     let cid = map.id();
     let id = a.get_list("list").get(1);
-    assert_eq!(id.unwrap().as_container().unwrap(), &cid);
+    assert_eq!(id.as_ref().unwrap().as_container().unwrap(), &cid);
+    let map = a.get_map(id.unwrap().into_container().unwrap());
+    let new_pos = a.get_map(map.get("pos").unwrap().into_container().unwrap());
+    assert_eq!(
+        new_pos.get_deep_value().to_json_value(),
+        json!({
+            "x": 0,
+            "y": 100,
+        })
+    );
 }
 
 #[test]
diff --git a/crates/loro-wasm/src/lib.rs b/crates/loro-wasm/src/lib.rs
index 6a972683..6c7ce500 100644
--- a/crates/loro-wasm/src/lib.rs
+++ b/crates/loro-wasm/src/lib.rs
@@ -154,7 +154,10 @@ fn js_value_to_container_id(
     kind: ContainerType,
 ) -> Result<ContainerID, JsValue> {
     if !cid.is_string() {
-        return Err(JsValue::from_str("ContainerID must be a string"));
+        return Err(JsValue::from_str(&format!(
+            "ContainerID must be a string, but found {}",
+            cid.js_typeof().as_string().unwrap(),
+        )));
     }
 
     let s = cid.as_string().unwrap();