diff --git a/lib/gitlab/markdown.rb b/lib/gitlab/markdown.rb
index ba993abf..fab89d09 100644
--- a/lib/gitlab/markdown.rb
+++ b/lib/gitlab/markdown.rb
@@ -173,7 +173,7 @@ module Gitlab
     end
 
     def reference_commit(identifier)
-      if commit = @project.commit(identifier)
+      if @project.valid_repo? && commit = @project.commit(identifier)
         link_to(identifier, project_commit_path(@project, commit), html_options.merge(title: CommitDecorator.new(commit).link_title, class: "gfm gfm-commit #{html_options[:class]}"))
       end
     end