diff --git a/oauth3.core.js b/oauth3.core.js
index 1328160..2af6f37 100644
--- a/oauth3.core.js
+++ b/oauth3.core.js
@@ -224,6 +224,13 @@
     var type = 'access_token';
     var grantType = 'password';
 
+    if (!passphrase) {
+      if (opts.otp) {
+        // for backwards compat
+        passphrase = opts.otp; // 'otp:' + opts.otpUuid + ':' + opts.otp;
+      }
+    }
+
     var scope = opts.scope || directive.authn_scope;
     var clientId = opts.appId;
     var clientAgreeTos = opts.clientAgreeTos;
@@ -232,8 +239,6 @@
     var params = {
       "grant_type": grantType
     , "username": username
-      // ('otp:' + opts.otpUuid + ':' + opts.otp)) // for backwards compat?
-      // ('totp:' + opts.totp) // for backwards compat?
     , "password": passphrase || undefined
     , "totp": opts.totp || opts.totpToken || undefined
     , "otp": opts.otp || opts.otpCode || undefined