diff --git a/mod/lti/OAuth.php b/mod/lti/OAuth.php
index 47bb8cddf8f..65e9b0f138a 100644
--- a/mod/lti/OAuth.php
+++ b/mod/lti/OAuth.php
@@ -181,7 +181,7 @@ class OAuthSignatureMethod_RSA_SHA1 extends OAuthSignatureMethod {
         // (3) some sort of specific discovery code based on request
         //
         // either way should return a string representation of the certificate
-        throw Exception("fetch_public_cert not implemented");
+        throw OAuthException("fetch_public_cert not implemented");
     }
 
     protected function fetch_private_cert(&$request) {
@@ -189,7 +189,7 @@ class OAuthSignatureMethod_RSA_SHA1 extends OAuthSignatureMethod {
         // (1) do a lookup in a table of trusted certs keyed off of consumer
         //
         // either way should return a string representation of the certificate
-        throw Exception("fetch_private_cert not implemented");
+        throw OAuthException("fetch_private_cert not implemented");
     }
 
     public function build_signature(&$request, $consumer, $token) {