diff --git a/lib/php/src/Thrift.php b/lib/php/src/Thrift.php
index ab56eff..8118e3b 100644
--- a/lib/php/src/Thrift.php
+++ b/lib/php/src/Thrift.php
@@ -29,6 +29,7 @@
 class TMessageType {
   const CALL  = 1;
   const REPLY = 2;
+  const EXCEPTION = 3;
 }
 
 class TException extends Exception {