diff --git a/vm/src/obj/objenumerate.rs b/vm/src/obj/objenumerate.rs
index 4bbe8caccf..3c6c864c2e 100644
--- a/vm/src/obj/objenumerate.rs
+++ b/vm/src/obj/objenumerate.rs
@@ -1,5 +1,5 @@
-use std::cell::RefCell;
 use std::ops::AddAssign;
+use std::sync::RwLock;
 
 use num_bigint::BigInt;
 use num_traits::Zero;
@@ -8,16 +8,17 @@ use super::objint::PyIntRef;
 use super::objiter;
 use super::objtype::PyClassRef;
 use crate::function::OptionalArg;
-use crate::pyobject::{PyClassImpl, PyContext, PyObjectRef, PyRef, PyResult, PyValue};
+use crate::pyobject::{PyClassImpl, PyContext, PyObjectRef, PyRef, PyResult, PyValue, ThreadSafe};
 use crate::vm::VirtualMachine;
 
 #[pyclass]
 #[derive(Debug)]
 pub struct PyEnumerate {
-    counter: RefCell<BigInt>,
+    counter: RwLock<BigInt>,
     iterator: PyObjectRef,
 }
 type PyEnumerateRef = PyRef<PyEnumerate>;
+impl ThreadSafe for PyEnumerate {}
 
 impl PyValue for PyEnumerate {
     fn class(vm: &VirtualMachine) -> PyClassRef {
@@ -41,24 +42,19 @@ impl PyEnumerate {
 
         let iterator = objiter::get_iter(vm, &iterable)?;
         PyEnumerate {
-            counter: RefCell::new(counter),
+            counter: RwLock::new(counter),
             iterator,
         }
         .into_ref_with_type(vm, cls)
     }
 
     #[pymethod(name = "__next__")]
-    fn next(&self, vm: &VirtualMachine) -> PyResult {
-        let iterator = &self.iterator;
-        let counter = &self.counter;
-        let next_obj = objiter::call_next(vm, iterator)?;
-        let result = vm
-            .ctx
-            .new_tuple(vec![vm.ctx.new_bigint(&counter.borrow()), next_obj]);
-
-        AddAssign::add_assign(&mut counter.borrow_mut() as &mut BigInt, 1);
-
-        Ok(result)
+    fn next(&self, vm: &VirtualMachine) -> PyResult<(BigInt, PyObjectRef)> {
+        let next_obj = objiter::call_next(vm, &self.iterator)?;
+        let mut counter = self.counter.write().unwrap();
+        let position = counter.clone();
+        AddAssign::add_assign(&mut counter as &mut BigInt, 1);
+        Ok((position, next_obj))
     }
 
     #[pymethod(name = "__iter__")]