diff --git a/Rakefile b/Rakefile
index 6cea33fa55..3aedf2799b 100644
--- a/Rakefile
+++ b/Rakefile
@@ -77,6 +77,7 @@ end
 def generate_src(target_version:)
   copy_sources = Dir.glob('rails/doc/rdoc/*').reject { |path| path.end_with?('panel', 'js', 'created.rid') }
   target_dir = target_version == default_rails_version ? SOURCE_DIR : "#{SOURCE_DIR}/#{target_version}"
+  remove_existing_files(target_dir)
   cp_r copy_sources, target_dir
 
   cd target_dir do
@@ -92,3 +93,10 @@ def generate_src(target_version:)
     File.write('navigation.html', content)
   end
 end
+
+EXISTING_DIRS = %w[classes files].freeze
+def remove_existing_files(target_dir)
+  EXISTING_DIRS.each do |dir|
+    rm_rf "#{target_dir}/#{dir}"
+  end
+end