diff --git a/xos/xos/exceptions.py b/xos/xos/exceptions.py
index 8d4464e..c13de49 100644
--- a/xos/xos/exceptions.py
+++ b/xos/xos/exceptions.py
@@ -34,6 +34,13 @@
                             "specific_error": why,
                             "fields": fields})
 
+class XOSMissingField(APIException):
+    status_code=400
+    def __init__(self, why="missing field", fields={}):
+        APIException.__init__(self, {"error": "XOSMissingField",
+                            "specific_error": why,
+                            "fields": fields})
+
 class XOSConfigurationError(APIException):
     status_code=400
     def __init__(self, why="configuration error", fields={}):