diff --git a/src/interface/common.thrift b/src/interface/common.thrift
index 8b55a4e4030..9d00fd57475 100644
--- a/src/interface/common.thrift
+++ b/src/interface/common.thrift
@@ -95,6 +95,7 @@ enum NullType {
     BAD_DATA = 2,
     BAD_TYPE = 3,
     ERR_OVERFLOW = 4,
+    UNKNOWN_PROP = 5,  // deprecated but not to be deleted
     DIV_BY_ZERO = 6,
     OUT_OF_RANGE = 7,
 } (cpp.enum_strict, cpp.type = "nebula::NullType")