diff --git a/phpserialize.py b/phpserialize.py
index 036cfb4..de62f78 100644
--- a/phpserialize.py
+++ b/phpserialize.py
@@ -507,7 +507,7 @@ def _unserialize():
             if decode_strings:
                 name = name.decode(charset, errors)
             return object_hook(name, dict(_load_array()))
-        raise ValueError('unexpected opcode')
+        raise ValueError('unexpected opcode - %s' % repr(type_))
 
     return _unserialize()