diff --git a/lib/net/imap/command_data.rb b/lib/net/imap/command_data.rb
index a0e04edb..1fd0dc30 100644
--- a/lib/net/imap/command_data.rb
+++ b/lib/net/imap/command_data.rb
@@ -58,7 +58,7 @@ def send_data(data, tag = nil)
       end
     end
 
-    UNQUOTABLE_CHARS = /\0\r\n/
+    UNQUOTABLE_CHARS = /[\0\r\n]/
     ASTRING_SPECIALS = /[(){ \x00-\x1f\x7f%*"\\]/
     private_constant :UNQUOTABLE_CHARS, :ASTRING_SPECIALS
 
diff --git a/test/net/imap/test_imap.rb b/test/net/imap/test_imap.rb
index d005bc50..b178681c 100644
--- a/test/net/imap/test_imap.rb
+++ b/test/net/imap/test_imap.rb
@@ -1045,6 +1045,10 @@ def imap.test_args(*args) = send_command("TEST", *args)
       send_args.call ["\xDE\xAD\xBE\xEF".b]
       assert_equal "({4}\r\n\xDE\xAD\xBE\xEF)".b, server.commands.pop.args
 
+      send_args.call ["hi\rthere\n", "huh?\r\nfake out"]
+      assert_equal "({9}\r\nhi\rthere\n {14}\r\nhuh?\r\nfake out)".b,
+                   server.commands.pop.args
+
       # enable automatic non-synchronizing literals
       imap.config.max_non_synchronizing_literal = 1024
       buff = bytes = nil