diff --git a/lib/client/client.js b/lib/client/client.js
index a765735..6dc9cde 100644
--- a/lib/client/client.js
+++ b/lib/client/client.js
@@ -454,8 +454,8 @@ Client.prototype.exop = function exop(name, value, controls, callback) {
     controls = [];
     value = '';
   }
-  if (typeof (value) !== 'string')
-    throw new TypeError('value (string) required');
+  if (!(Buffer.isBuffer(value) || typeof (value) === 'string'))
+    throw new TypeError('value (Buffer || string) required');
   if (typeof (controls) === 'function') {
     callback = controls;
     controls = [];