diff --git a/lib/csv/parser.rb b/lib/csv/parser.rb
index 25f10df..d38a8d5 100644
--- a/lib/csv/parser.rb
+++ b/lib/csv/parser.rb
@@ -417,6 +417,7 @@ def parse(&block)
         if @unconverted_fields
           headers = add_unconverted_fields(headers, [])
         end
+        @raw_headers = nil
         yield headers
       end