diff --git a/tensorflow_privacy/privacy/membership_inference_attack/privacy_report.py b/tensorflow_privacy/privacy/membership_inference_attack/privacy_report.py
index e05774a..a2cb56f 100644
--- a/tensorflow_privacy/privacy/membership_inference_attack/privacy_report.py
+++ b/tensorflow_privacy/privacy/membership_inference_attack/privacy_report.py
@@ -134,5 +134,5 @@ def _validate_results(results: Iterable[AttackResults]):
   for attack_results in results:
     if not attack_results or not attack_results.privacy_report_metadata:
       raise ValueError('Privacy metadata is not defined.')
-    if not attack_results.privacy_report_metadata.epoch_num:
+    if attack_results.privacy_report_metadata.epoch_num is None:
       raise ValueError('epoch_num in metadata is not defined.')
diff --git a/tensorflow_privacy/privacy/membership_inference_attack/privacy_report_test.py b/tensorflow_privacy/privacy/membership_inference_attack/privacy_report_test.py
index 8b3bdf2..326cad0 100644
--- a/tensorflow_privacy/privacy/membership_inference_attack/privacy_report_test.py
+++ b/tensorflow_privacy/privacy/membership_inference_attack/privacy_report_test.py
@@ -52,6 +52,14 @@ class PrivacyReportTest(absltest.TestCase):
             fpr=np.array([1.0, 1.0, 0.0]),
             thresholds=np.array([0, 1, 2])))
 
+    self.results_epoch_0 = AttackResults(
+        single_attack_results=[self.imperfect_classifier_result],
+        privacy_report_metadata=PrivacyReportMetadata(
+            accuracy_train=0.4,
+            accuracy_test=0.3,
+            epoch_num=0,
+            model_variant_label='default'))
+
     self.results_epoch_10 = AttackResults(
         single_attack_results=[self.imperfect_classifier_result],
         privacy_report_metadata=PrivacyReportMetadata(
@@ -87,14 +95,14 @@ class PrivacyReportTest(absltest.TestCase):
 
   def test_single_metric_plot_by_epochs(self):
     fig = privacy_report.plot_by_epochs(
-        AttackResultsCollection((self.results_epoch_10, self.results_epoch_15)),
-        ['AUC'])
+        AttackResultsCollection((self.results_epoch_0, self.results_epoch_10,
+                                 self.results_epoch_15)), ['AUC'])
     # extract data from figure.
     auc_data = fig.gca().lines[0].get_data()
     # X axis lists epoch values
-    np.testing.assert_array_equal(auc_data[0], [10, 15])
+    np.testing.assert_array_equal(auc_data[0], [0, 10, 15])
     # Y axis lists AUC values
-    np.testing.assert_array_equal(auc_data[1], [0.5, 1.0])
+    np.testing.assert_array_equal(auc_data[1], [0.5, 0.5, 1.0])
     # Check the title
     self.assertEqual(fig._suptitle.get_text(), 'Vulnerability per Epoch')