diff --git a/lm_optimizer.py b/lm_optimizer.py
index 78215682..25d8a05e 100644
--- a/lm_optimizer.py
+++ b/lm_optimizer.py
@@ -27,11 +27,23 @@ def objective(trial):
     FLAGS.lm_alpha = trial.suggest_uniform('lm_alpha', 0, FLAGS.lm_alpha_max)
     FLAGS.lm_beta = trial.suggest_uniform('lm_beta', 0, FLAGS.lm_beta_max)
 
-    tfv1.reset_default_graph()
-    samples = evaluate(FLAGS.test_files.split(','), create_model)
-
     is_character_based = trial.study.user_attrs['is_character_based']
 
+    samples = []
+    for step, test_file in enumerate(FLAGS.test_files.split(',')):
+        tfv1.reset_default_graph()
+
+        current_samples = evaluate([test_file], create_model)
+        samples += current_samples
+
+        # Report intermediate objective value.
+        wer, cer = wer_cer_batch(current_samples)
+        trial.report(cer if is_character_based else wer, step)
+
+        # Handle pruning based on the intermediate value.
+        if trial.should_prune():
+            raise optuna.exceptions.TrialPruned()
+
     wer, cer = wer_cer_batch(samples)
     return cer if is_character_based else wer