diff --git a/activesupport/lib/active_support/dependencies.rb b/activesupport/lib/active_support/dependencies.rb
index 1b93eac7ee667538bcd8318caeee88e909b7bf43..198c124292a80179214fc74a8256db1d9c682f2c 100644
--- a/activesupport/lib/active_support/dependencies.rb
+++ b/activesupport/lib/active_support/dependencies.rb
@@ -388,8 +388,13 @@ def loadable_constants_for_path(path, bases = autoload_paths)
     end
 
     # Search for a file in autoload_paths matching the provided suffix.
-    def search_for_file(path_suffix)
-      path_suffix = path_suffix.sub(/(\.rb)?$/, ".rb")
+    def search_for_file(file)
+      path_suffix = file.sub(/(\.rb)?$/, ".rb")
+
+      $:.each do |root|
+        path = File.join(root, path_suffix)
+        return file if File.file?(path)
+      end
 
       autoload_paths.each do |root|
         path = File.join(root, path_suffix)