diff --git a/lib/csv/writer.rb b/lib/csv/writer.rb
index b59f111..c6233fc 100644
--- a/lib/csv/writer.rb
+++ b/lib/csv/writer.rb
@@ -153,6 +153,7 @@ def prepare_format
         @quotable_pattern =
           Regexp.new("[\r\n".encode(@encoding) +
                      Regexp.escape(@column_separator) +
+                     Regexp.escape(@row_separator) +
                      Regexp.escape(@quote_character.encode(@encoding)) +
                      "]".encode(@encoding))
       end