diff --git a/judges/github-events/github-events.rb b/judges/github-events/github-events.rb
index aa2fa23e..3cd2cd16 100644
--- a/judges/github-events/github-events.rb
+++ b/judges/github-events/github-events.rb
@@ -49,7 +49,8 @@ def self.fetch_contributors(fact, repo)
     contributors = Set.new
     if last
       Fbe.octo.compare(repo, last.tag, fact.tag)[:commits].each do |commit|
-        contributors << commit[:author][:id]
+        author_id = commit.dig(:author, :id)
+        contributors << author_id if author_id
       end
     else
       Fbe.octo.contributors(repo).each do |contributor|
diff --git a/test/judges/test-github-events.rb b/test/judges/test-github-events.rb
index 2509fd9a..9e2d74ae 100644
--- a/test/judges/test-github-events.rb
+++ b/test/judges/test-github-events.rb
@@ -879,7 +879,10 @@ def test_release_event_contributors
           { sha: 'a50489ead5e8aa6', author: { login: 'Yegorov', id: 2_566_462 } },
           { sha: 'b50489ead5e8aa7', author: { login: 'Yegorov64', id: 2_566_463 } },
           { sha: 'c50489ead5e8aa8', author: { login: 'Yegorov128', id: 2_566_464 } },
-          { sha: 'd50489ead5e8aa9', author: { login: 'Yegorov', id: 2_566_462 } }
+          { sha: 'd50489ead5e8aa9', author: { login: 'Yegorov', id: 2_566_462 } },
+          { sha: 'e50489ead5e8aa9', author: nil },
+          { sha: 'e60489ead5e8aa9' },
+          { sha: 'e70489ead5e8aa9', author: { login: 'NoUser' } }
         ],
         files: [
           { additions: 15, deletions: 40, changes: 55 },