diff --git a/app/models.py b/app/models.py
index 1592557b6..4effde3c6 100644
--- a/app/models.py
+++ b/app/models.py
@@ -464,7 +464,7 @@ class Template(db.Model):
             "created_by": self.created_by.email_address,
             "version": self.version,
             "body": self.content,
-            "subject": self.subject if self.template_type == EMAIL_TYPE else None
+            "subject": self.subject if self.template_type != SMS_TYPE else None
         }
 
         return serialized
diff --git a/tests/app/test_model.py b/tests/app/test_model.py
index 9cefb66df..d38e641ab 100644
--- a/tests/app/test_model.py
+++ b/tests/app/test_model.py
@@ -203,3 +203,18 @@ def test_letter_notification_serializes_with_address(client, sample_letter_notif
     assert res['line_5'] is None
     assert res['line_6'] is None
     assert res['postcode'] == 'SW1 1AA'
+
+
+def test_sms_notification_serializes_without_subject(client, sample_template):
+    res = sample_template.serialize()
+    assert res['subject'] is None
+
+
+def test_email_notification_serializes_with_subject(client, sample_email_template):
+    res = sample_email_template.serialize()
+    assert res['subject'] == 'Email Subject'
+
+
+def test_letter_notification_serializes_with_subject(client, sample_letter_template):
+    res = sample_letter_template.serialize()
+    assert res['subject'] == 'Template Subject'