diff --git a/app/models/merge_request.rb b/app/models/merge_request.rb
index 926944bc3b3..70005a87f4b 100644
--- a/app/models/merge_request.rb
+++ b/app/models/merge_request.rb
@@ -221,7 +221,7 @@ class MergeRequest < ActiveRecord::Base
   # true base commit, so we can't simply have `#diff_base_commit` fall back on
   # this method.
   def likely_diff_base_commit
-    first_commit.parent || first_commit
+    first_commit.try(:parent) || first_commit
   end
 
   def diff_start_commit