diff --git a/reviewboard/diffviewer/models/diffcommit.py b/reviewboard/diffviewer/models/diffcommit.py
index 8e2d9587bc8b5e8e44edaf253b9e560018ce9fc2..cbe7ede93da970412528e9a16fd736d4f51db19c 100644
--- a/reviewboard/diffviewer/models/diffcommit.py
+++ b/reviewboard/diffviewer/models/diffcommit.py
@@ -169,7 +169,7 @@ class DiffCommit(FileDiffCollectionMixin, models.Model):
     @cached_property
     def summary(self):
         """The first line of the commit message."""
-        summary = self.description
+        summary = self.commit_message
 
         if summary:
             summary = summary.split('\n', 1)[0].strip()