diff --git a/lib/Connection.js b/lib/Connection.js
index f33ef4b..4b2cd5c 100644
--- a/lib/Connection.js
+++ b/lib/Connection.js
@@ -259,8 +259,13 @@ Connection.prototype.append = function(data, options, cb) {
   if (options.flags) {
     if (!Array.isArray(options.flags))
       options.flags = [options.flags];
-    if (options.flags.length > 0)
-      cmd += ' (\\' + options.flags.join(' \\') + ')';
+    if (options.flags.length > 0) {
+      for (var i = 0, len = options.flags.length; i < len; ++i) {
+        if (options.flags[i][0] !== '\\')
+          options.flags[i] = '\\' + options.flags[i];
+      }
+      cmd += ' (' + options.flags.join(' ') + ')';
+    }
   }
   if (options.date) {
     if (!isDate(options.date))