diff --git a/lib/yard/code_objects/base.rb b/lib/yard/code_objects/base.rb
index 27b37e549..fed0957d3 100644
--- a/lib/yard/code_objects/base.rb
+++ b/lib/yard/code_objects/base.rb
@@ -303,6 +303,7 @@ def add_file(file, line = nil, has_comments = false)
       # definitions with docstrings first.
       #
       # @return [String] a filename
+      # @return [nil] if there is no file associated with the object
       def file
         @files.first ? @files.first[0] : nil
       end