diff --git a/vm/src/builtins/pyunion.rs b/vm/src/builtins/pyunion.rs
index fb4e1d28b4..5006822040 100644
--- a/vm/src/builtins/pyunion.rs
+++ b/vm/src/builtins/pyunion.rs
@@ -41,7 +41,7 @@ impl PyUnion {
     #[pymethod(magic)]
     fn repr(&self, vm: &VirtualMachine) -> PyResult<String> {
         fn repr_item(obj: PyObjectRef, vm: &VirtualMachine) -> PyResult<String> {
-            if obj.is(&vm.ctx.types.none_type) {
+            if vm.is_none(&obj) {
                 return Ok("None".to_string());
             }