diff --git a/weaseljson.py b/weaseljson.py
index 7063c98..777d8fe 100644
--- a/weaseljson.py
+++ b/weaseljson.py
@@ -30,6 +30,7 @@ class WeaselJsonStatus(enum.Enum):
     AGAIN = 1
     REJECT = 2
     OVERFLOW = 3
+    NULL = 4
 
 
 class WeaselJsonCallbacksBase: