diff --git a/compiler/can/src/builtins.rs b/compiler/can/src/builtins.rs
index 8704cfd6d7..6ca4a083e4 100644
--- a/compiler/can/src/builtins.rs
+++ b/compiler/can/src/builtins.rs
@@ -78,7 +78,7 @@ fn list_get(var_store: &VarStore) -> Def {
                 // Ok
                 Tag {
                     variant_var: var_store.fresh(),
-                    ext_var: var_store.fresh(),
+                    ext_var: var_store.fresh(), // TODO Variable::EMPTY_TAG_UNION should work here
                     name: TagName::Global("Ok".into()),
                     arguments: vec![(
                         var_store.fresh(),