diff --git a/test/ruby/test_gc_compact.rb b/test/ruby/test_gc_compact.rb
index 84828d498543aa..7e0c499dd9c82c 100644
--- a/test/ruby/test_gc_compact.rb
+++ b/test/ruby/test_gc_compact.rb
@@ -324,7 +324,7 @@ def test_moving_arrays_up_heaps
       }.resume
 
       stats = GC.verify_compaction_references(expand_heap: true, toward: :empty)
-      assert_operator(stats.dig(:moved_up, :T_ARRAY) || 0, :>=, ARY_COUNT - 15)
+      assert_operator(stats.dig(:moved_up, :T_ARRAY) || 0, :>=, (0.9995 * ARY_COUNT).to_i)
       refute_empty($arys.keep_if { |o| ObjectSpace.dump(o).include?('"embedded":true') })
     end;
   end
diff --git a/tool/lib/vcs.rb b/tool/lib/vcs.rb
index 4f6dc0043283e8..6ebfb9e93b81ad 100644
--- a/tool/lib/vcs.rb
+++ b/tool/lib/vcs.rb
@@ -448,9 +448,11 @@ def export(revision, url, dir, keep_temp = false)
     end
 
     def branch_beginning(url)
-      cmd_read(%W[ #{COMMAND} log -n1 --format=format:%H
+      files = %w[version.h include/ruby/version.h]
+      year = cmd_read(%W[ #{COMMAND} log -n1 --format=%cd --date=format:%Y #{url} --] + files).to_i
+      cmd_read(%W[ #{COMMAND} log --format=format:%H --reverse --since=#{year-1}-12-25
                    --author=matz --committer=matz --grep=started\\.$
-                   #{url.to_str} -- version.h include/ruby/version.h])
+                   #{url} --] + files)[/.*/]
     end
 
     def export_changelog(url = '@', from = nil, to = nil, _path = nil, path: _path, base_url: true)