diff --git a/extlib/OAuth.php b/extlib/OAuth.php
index 9dc9a99b75..60c50f1cea 100644
--- a/extlib/OAuth.php
+++ b/extlib/OAuth.php
@@ -3,8 +3,10 @@
 
 /* Generic exception class
  */
-class OAuthException extends Exception {
-  // pass
+if (!class_exists(OAuthException)) {
+  class OAuthException extends Exception {
+    // pass
+  }
 }
 
 class OAuthConsumer {