diff --git a/lib/ruby_indexer/lib/ruby_indexer/configuration.rb b/lib/ruby_indexer/lib/ruby_indexer/configuration.rb
index 7e102e3ca..368c9177c 100644
--- a/lib/ruby_indexer/lib/ruby_indexer/configuration.rb
+++ b/lib/ruby_indexer/lib/ruby_indexer/configuration.rb
@@ -134,7 +134,7 @@ def files_to_index
 
     sig { returns(Regexp) }
     def magic_comment_regex
-      /^\s*#\s*#{@excluded_magic_comments.join("|")}/
+      @magic_comment_regex ||= T.let(/^\s*#\s*#{@excluded_magic_comments.join("|")}/, T.nilable(Regexp))
     end
 
     private