diff --git a/research/object_detection/model_lib.py b/research/object_detection/model_lib.py
index 5ba6f9b6538..2239bb8b049 100644
--- a/research/object_detection/model_lib.py
+++ b/research/object_detection/model_lib.py
@@ -411,7 +411,7 @@ def tpu_scaffold():
 
       # Eval metrics on a single example.
       eval_metric_ops = eval_util.get_eval_metric_ops_for_evaluators(
-          eval_config, category_index.values(), eval_dict)
+          eval_config, list(category_index.values()), eval_dict)
       for loss_key, loss_tensor in iter(losses_dict.items()):
         eval_metric_ops[loss_key] = tf.metrics.mean(loss_tensor)
       for var in optimizer_summary_vars: