diff --git a/lib/opencnam.js b/lib/opencnam.js
index 3dfe9d0..7448214 100644
--- a/lib/opencnam.js
+++ b/lib/opencnam.js
@@ -36,7 +36,13 @@ exports.lookup = function(phone_number, options, callback) {
     return callback(new Error('phone_number must be 10 digits.'));
   }
 
-  var uri = OPENCNAM_API_URI + phone_number + '?format=text';
+  var format = 'format=text';
+
+  if (options.format) {
+    format = 'format=' + options.format;
+  }
+
+  var uri = OPENCNAM_API_URI + phone_number + '?' + format;
 
   if (options.account_sid) {
     uri += '&account_sid=' + encodeURIComponent(options.account_sid);