diff --git a/src/codec/RowReaderV1.cpp b/src/codec/RowReaderV1.cpp
index 877e1e35cee..b56b831a228 100644
--- a/src/codec/RowReaderV1.cpp
+++ b/src/codec/RowReaderV1.cpp
@@ -198,11 +198,11 @@ Value RowReaderV1::getValueByName(const std::string& prop) const noexcept {
 
 Value RowReaderV1::getValueByIndex(const int64_t index) const noexcept {
   if (index < 0 || static_cast<size_t>(index) >= schema_->getNumFields()) {
-    return Value(NullType::UNKNOWN_PROP);
+    return Value(NullType::__NULL__);
   }
   auto vType = getSchema()->getFieldType(index);
   if (PropertyType::UNKNOWN == vType) {
-    return Value(NullType::UNKNOWN_PROP);
+    return Value(NullType::__NULL__);
   }
   switch (vType) {
     case PropertyType::BOOL:
diff --git a/src/codec/RowReaderV2.cpp b/src/codec/RowReaderV2.cpp
index fc213cbf568..91db3933fec 100644
--- a/src/codec/RowReaderV2.cpp
+++ b/src/codec/RowReaderV2.cpp
@@ -52,7 +52,7 @@ Value RowReaderV2::getValueByName(const std::string& prop) const noexcept {
 
 Value RowReaderV2::getValueByIndex(const int64_t index) const noexcept {
   if (index < 0 || static_cast<size_t>(index) >= schema_->getNumFields()) {
-    return Value(NullType::UNKNOWN_PROP);
+    return Value(NullType::__NULL__);
   }
 
   auto field = schema_->field(index);
diff --git a/src/common/datatypes/Map.h b/src/common/datatypes/Map.h
index 91134a48387..9a55f28318c 100644
--- a/src/common/datatypes/Map.h
+++ b/src/common/datatypes/Map.h
@@ -69,7 +69,7 @@ struct Map {
   const Value& at(const std::string& key) const {
     auto iter = kvs.find(key);
     if (iter == kvs.end()) {
-      return Value::kNullUnknownProp;
+      return Value::kNullValue;
     }
     return iter->second;
   }
diff --git a/src/common/datatypes/Value.cpp b/src/common/datatypes/Value.cpp
index 7de3ece5103..c49adf90290 100644
--- a/src/common/datatypes/Value.cpp
+++ b/src/common/datatypes/Value.cpp
@@ -29,7 +29,6 @@ const Value Value::kNullNaN(NullType::NaN);
 const Value Value::kNullBadData(NullType::BAD_DATA);
 const Value Value::kNullBadType(NullType::BAD_TYPE);
 const Value Value::kNullOverflow(NullType::ERR_OVERFLOW);
-const Value Value::kNullUnknownProp(NullType::UNKNOWN_PROP);
 const Value Value::kNullDivByZero(NullType::DIV_BY_ZERO);
 const Value Value::kNullOutOfRange(NullType::OUT_OF_RANGE);
 
@@ -320,7 +319,6 @@ const std::string& Value::typeName() const {
       {NullType::BAD_DATA, "BAD_DATA"},
       {NullType::BAD_TYPE, "BAD_TYPE"},
       {NullType::ERR_OVERFLOW, "ERR_OVERFLOW"},
-      {NullType::UNKNOWN_PROP, "UNKNOWN_PROP"},
       {NullType::DIV_BY_ZERO, "DIV_BY_ZERO"},
   };
 
@@ -1564,8 +1562,6 @@ std::string Value::toString() const {
           return "__NULL_OVERFLOW__";
         case NullType::NaN:
           return "__NULL_NaN__";
-        case NullType::UNKNOWN_PROP:
-          return "__NULL_UNKNOWN_PROP__";
         case NullType::OUT_OF_RANGE:
           return "__NULL_OUT_OF_RANGE__";
       }
diff --git a/src/common/datatypes/Value.h b/src/common/datatypes/Value.h
index 06f4e8b2241..b55397a1566 100644
--- a/src/common/datatypes/Value.h
+++ b/src/common/datatypes/Value.h
@@ -40,7 +40,6 @@ enum class NullType {
   BAD_DATA = 2,
   BAD_TYPE = 3,
   ERR_OVERFLOW = 4,
-  UNKNOWN_PROP = 5,
   DIV_BY_ZERO = 6,
   OUT_OF_RANGE = 7,
 };
@@ -52,7 +51,6 @@ struct Value {
   static const Value kNullBadData;
   static const Value kNullBadType;
   static const Value kNullOverflow;
-  static const Value kNullUnknownProp;
   static const Value kNullDivByZero;
   static const Value kNullOutOfRange;
 
@@ -157,8 +155,8 @@ struct Value {
     }
     auto& null = value_.nVal;
     return null == NullType::NaN || null == NullType::BAD_DATA || null == NullType::BAD_TYPE ||
-           null == NullType::ERR_OVERFLOW || null == NullType::UNKNOWN_PROP ||
-           null == NullType::DIV_BY_ZERO || null == NullType::OUT_OF_RANGE;
+           null == NullType::ERR_OVERFLOW || null == NullType::DIV_BY_ZERO ||
+           null == NullType::OUT_OF_RANGE;
   }
   bool isNumeric() const {
     return type_ == Type::INT || type_ == Type::FLOAT;
diff --git a/src/common/datatypes/test/ValueTest.cpp b/src/common/datatypes/test/ValueTest.cpp
index 73abce84640..571c74f463f 100644
--- a/src/common/datatypes/test/ValueTest.cpp
+++ b/src/common/datatypes/test/ValueTest.cpp
@@ -1565,7 +1565,6 @@ TEST(Value, typeName) {
   EXPECT_EQ("BAD_DATA", Value::kNullBadData.typeName());
   EXPECT_EQ("BAD_TYPE", Value::kNullBadType.typeName());
   EXPECT_EQ("ERR_OVERFLOW", Value::kNullOverflow.typeName());
-  EXPECT_EQ("UNKNOWN_PROP", Value::kNullUnknownProp.typeName());
   EXPECT_EQ("DIV_BY_ZERO", Value::kNullDivByZero.typeName());
 }
 
@@ -1582,7 +1581,6 @@ TEST(Value, DecodeEncode) {
       Value(NullType::BAD_DATA),
       Value(NullType::ERR_OVERFLOW),
       Value(NullType::OUT_OF_RANGE),
-      Value(NullType::UNKNOWN_PROP),
 
       // int
       Value(0),
diff --git a/src/common/datatypes/test/ValueToJsonTest.cpp b/src/common/datatypes/test/ValueToJsonTest.cpp
index 457b666051d..a2e8923e2a5 100644
--- a/src/common/datatypes/test/ValueToJsonTest.cpp
+++ b/src/common/datatypes/test/ValueToJsonTest.cpp
@@ -225,7 +225,7 @@ TEST(ValueToJson, DecodeEncode) {
       Value(NullType::BAD_DATA),
       Value(NullType::ERR_OVERFLOW),
       Value(NullType::OUT_OF_RANGE),
-      Value(NullType::UNKNOWN_PROP),
+      Value(NullType::__NULL__),
 
       // int
       Value(0),
diff --git a/src/common/expression/AttributeExpression.cpp b/src/common/expression/AttributeExpression.cpp
index 92425be7892..4f8f7b9c147 100644
--- a/src/common/expression/AttributeExpression.cpp
+++ b/src/common/expression/AttributeExpression.cpp
@@ -33,7 +33,7 @@ const Value &AttributeExpression::eval(ExpressionContext &ctx) {
           return iter->second;
         }
       }
-      return Value::kNullUnknownProp;
+      return Value::kNullValue;
     }
     case Value::Type::EDGE: {
       DCHECK(!rvalue.getStr().empty());
diff --git a/src/common/expression/test/AttributeExpressionTest.cpp b/src/common/expression/test/AttributeExpressionTest.cpp
index 5b3dbbe5870..1258e953bfa 100644
--- a/src/common/expression/test/AttributeExpressionTest.cpp
+++ b/src/common/expression/test/AttributeExpressionTest.cpp
@@ -134,7 +134,7 @@ TEST_F(AttributeExpressionTest, DateTimeAttribute) {
     auto *right = LabelExpression::make(&pool, "not exist attribute");
     auto expr = AttributeExpression::make(&pool, left, right);
     auto value = Expression::eval(expr, gExpCtxt);
-    ASSERT_EQ(Value::kNullUnknownProp, value);
+    ASSERT_EQ(Value::kNullValue, value);
   }
   {
     auto *left = ConstantExpression::make(&pool, Value(dt));
@@ -148,7 +148,7 @@ TEST_F(AttributeExpressionTest, DateTimeAttribute) {
     auto *right = LabelExpression::make(&pool, "not exist attribute");
     auto expr = AttributeExpression::make(&pool, left, right);
     auto value = Expression::eval(expr, gExpCtxt);
-    ASSERT_EQ(Value::kNullUnknownProp, value);
+    ASSERT_EQ(Value::kNullValue, value);
   }
   {
     auto *left = ConstantExpression::make(&pool, Value(d));
@@ -162,7 +162,7 @@ TEST_F(AttributeExpressionTest, DateTimeAttribute) {
     auto *right = LabelExpression::make(&pool, "not exist attribute");
     auto expr = AttributeExpression::make(&pool, left, right);
     auto value = Expression::eval(expr, gExpCtxt);
-    ASSERT_EQ(Value::kNullUnknownProp, value);
+    ASSERT_EQ(Value::kNullValue, value);
   }
   {
     auto *left = ConstantExpression::make(&pool, Value(t));
diff --git a/src/common/expression/test/SubscriptExpressionTest.cpp b/src/common/expression/test/SubscriptExpressionTest.cpp
index 622557d7b5a..7d7f7ead0cf 100644
--- a/src/common/expression/test/SubscriptExpressionTest.cpp
+++ b/src/common/expression/test/SubscriptExpressionTest.cpp
@@ -338,7 +338,6 @@ TEST_F(SubscriptExpressionTest, MapSubscript) {
     auto expr = SubscriptExpression::make(&pool, map, key);
     auto value = Expression::eval(expr, gExpCtxt);
     ASSERT_TRUE(value.isNull());
-    ASSERT_TRUE(value.isBadNull());
   }
   // {"key1":1,"key2":2, "key3":3}[0]
   {
diff --git a/src/common/time/TimeUtils.h b/src/common/time/TimeUtils.h
index 94570877ad3..e2c4bba09ed 100644
--- a/src/common/time/TimeUtils.h
+++ b/src/common/time/TimeUtils.h
@@ -124,7 +124,7 @@ class TimeUtils {
     } else if (lowerProp == "microsecond") {
       return static_cast<int>(dt.microsec);
     } else {
-      return Value::kNullUnknownProp;
+      return Value::kNullValue;
     }
   }
 
@@ -160,7 +160,7 @@ class TimeUtils {
     } else if (lowerProp == "day") {
       return d.day;
     } else {
-      return Value::kNullUnknownProp;
+      return Value::kNullValue;
     }
   }
 
@@ -203,7 +203,7 @@ class TimeUtils {
     } else if (lowerProp == "microsecond") {
       return t.microsec;
     } else {
-      return Value::kNullUnknownProp;
+      return Value::kNullValue;
     }
   }
 
diff --git a/src/common/utils/IndexKeyUtils.cpp b/src/common/utils/IndexKeyUtils.cpp
index 3707d85f52e..5e984ddb54e 100644
--- a/src/common/utils/IndexKeyUtils.cpp
+++ b/src/common/utils/IndexKeyUtils.cpp
@@ -204,7 +204,7 @@ StatusOr<Value> IndexKeyUtils::readValueWithLatestSche(RowReader* reader,
                                                        const std::string propName,
                                                        const meta::SchemaProviderIf* latestSchema) {
   auto value = reader->getValueByName(propName);
-  if (latestSchema == nullptr || !value.isNull() || value.getNull() != NullType::UNKNOWN_PROP) {
+  if (latestSchema == nullptr || !value.isNull() || value.getNull() != NullType::__NULL__) {
     return value;
   }
   auto field = latestSchema->field(propName);
@@ -230,9 +230,6 @@ Status IndexKeyUtils::checkValue(const Value& v, bool isNullable) {
   }
 
   switch (v.getNull()) {
-    case nebula::NullType::UNKNOWN_PROP: {
-      return Status::Error("Unknown prop");
-    }
     case nebula::NullType::__NULL__: {
       if (!isNullable) {
         return Status::Error("Not allowed to be null");
diff --git a/src/interface/common.thrift b/src/interface/common.thrift
index 808ffaf769f..8b55a4e4030 100644
--- a/src/interface/common.thrift
+++ b/src/interface/common.thrift
@@ -95,7 +95,6 @@ enum NullType {
     BAD_DATA = 2,
     BAD_TYPE = 3,
     ERR_OVERFLOW = 4,
-    UNKNOWN_PROP = 5,
     DIV_BY_ZERO = 6,
     OUT_OF_RANGE = 7,
 } (cpp.enum_strict, cpp.type = "nebula::NullType")
diff --git a/src/storage/exec/IndexEdgeScanNode.cpp b/src/storage/exec/IndexEdgeScanNode.cpp
index 9eb9fb26cb2..d4dcfd67ecd 100644
--- a/src/storage/exec/IndexEdgeScanNode.cpp
+++ b/src/storage/exec/IndexEdgeScanNode.cpp
@@ -122,7 +122,7 @@ Map<std::string, Value> IndexEdgeScanNode::decodeFromBase(const std::string& key
       case QueryUtils::ReturnColType::kOther: {
         auto field = edge_.back()->field(col);
         if (field == nullptr) {
-          values[col] = Value::kNullUnknownProp;
+          values[col] = Value::kNullValue;
         } else {
           auto retVal = QueryUtils::readValue(reader.get(), col, field);
           if (!retVal.ok()) {
diff --git a/src/storage/exec/IndexVertexScanNode.cpp b/src/storage/exec/IndexVertexScanNode.cpp
index 4dcfd01075c..fd2eed2ae0c 100644
--- a/src/storage/exec/IndexVertexScanNode.cpp
+++ b/src/storage/exec/IndexVertexScanNode.cpp
@@ -99,7 +99,7 @@ Map<std::string, Value> IndexVertexScanNode::decodeFromBase(const std::string& k
       case QueryUtils::ReturnColType::kOther: {
         auto field = tag_.back()->field(col);
         if (field == nullptr) {
-          values[col] = Value::kNullUnknownProp;
+          values[col] = Value::kNullValue;
         } else {
           auto retVal = QueryUtils::readValue(reader.get(), col, field);
           if (!retVal.ok()) {
diff --git a/src/storage/exec/QueryUtils.h b/src/storage/exec/QueryUtils.h
index 4a3c1499727..1fe1103cf17 100644
--- a/src/storage/exec/QueryUtils.h
+++ b/src/storage/exec/QueryUtils.h
@@ -79,7 +79,7 @@ class QueryUtils final {
       // read null value
       auto nullType = value.getNull();
 
-      if (nullType == NullType::UNKNOWN_PROP) {
+      if (nullType == NullType::__NULL__) {
         VLOG(1) << "Fail to read prop " << propName;
         if (!field) {
           return value;
diff --git a/src/tools/db-upgrade/DbUpgrader.cpp b/src/tools/db-upgrade/DbUpgrader.cpp
index c0834d87339..822f9cc7899 100644
--- a/src/tools/db-upgrade/DbUpgrader.cpp
+++ b/src/tools/db-upgrade/DbUpgrader.cpp
@@ -867,7 +867,7 @@ std::string UpgraderSpace::encodeRowVal(const RowReader* reader,
           LOG(ERROR) << "Write rowWriterV2 failed";
           return "";
         }
-      } else if (nullType != NullType::UNKNOWN_PROP) {
+      } else if (nullType != NullType::__NULL__) {
         // nullType == NullType::kNullUnknownProp, indicates that the field is
         // only in the latest schema, maybe use default value or null value.
         LOG(ERROR) << "Data is illegal in " << name << " field";
diff --git a/tests/common/nebula_test_suite.py b/tests/common/nebula_test_suite.py
index 83b746704b3..efc0c1f128c 100644
--- a/tests/common/nebula_test_suite.py
+++ b/tests/common/nebula_test_suite.py
@@ -34,8 +34,8 @@
 T_NULL_BAD_DATA.set_nVal(CommonTtypes.NullType.BAD_DATA)
 T_NULL_BAD_TYPE = CommonTtypes.Value()
 T_NULL_BAD_TYPE.set_nVal(CommonTtypes.NullType.BAD_TYPE)
-T_NULL_UNKNOWN_PROP = CommonTtypes.Value()
-T_NULL_UNKNOWN_PROP.set_nVal(CommonTtypes.NullType.UNKNOWN_PROP)
+T_NULL___NULL__ = CommonTtypes.Value()
+T_NULL___NULL__.set_nVal(CommonTtypes.NullType.__NULL__)
 T_NULL_UNKNOWN_DIV_BY_ZERO = CommonTtypes.Value()
 T_NULL_UNKNOWN_DIV_BY_ZERO.set_nVal(CommonTtypes.NullType.DIV_BY_ZERO)
 
diff --git a/tests/tck/features/expression/Attribute.feature b/tests/tck/features/expression/Attribute.feature
index c471c3554c4..bfff234892f 100644
--- a/tests/tck/features/expression/Attribute.feature
+++ b/tests/tck/features/expression/Attribute.feature
@@ -61,8 +61,8 @@ Feature: Attribute
       RETURN {k1 : 1, k2: true}.K1 AS k
       """
     Then the result should be, in any order:
-      | k            |
-      | UNKNOWN_PROP |
+      | k        |
+      | __NULL__ |
     When executing query:
       """
       MATCH (v) WHERE id(v) == 'Tim Duncan' RETURN v.player.name
@@ -101,28 +101,28 @@ Feature: Attribute
       """
     Then the result should be, in any order:
       | not_exists_attr |
-      | UNKNOWN_PROP    |
+      | __NULL__        |
     When executing query:
       """
       RETURN time("02:59:40").not_exists_attr AS not_exists_attr
       """
     Then the result should be, in any order:
       | not_exists_attr |
-      | UNKNOWN_PROP    |
+      | __NULL__        |
     When executing query:
       """
       RETURN datetime("2021-07-19T02:59:40").not_exists_attr AS not_exists_attr
       """
     Then the result should be, in any order:
       | not_exists_attr |
-      | UNKNOWN_PROP    |
+      | __NULL__        |
     When executing query:
       """
       RETURN {k1 : 1, k2: true}.not_exists_attr AS not_exists_attr
       """
     Then the result should be, in any order:
       | not_exists_attr |
-      | UNKNOWN_PROP    |
+      | __NULL__        |
     When executing query:
       """
       MATCH (v) WHERE id(v) == 'Tim Duncan' RETURN v.player.not_exists_attr
diff --git a/tests/tck/features/match/With.feature b/tests/tck/features/match/With.feature
index 8cf68f1edd1..9f76a59e9b7 100644
--- a/tests/tck/features/match/With.feature
+++ b/tests/tck/features/match/With.feature
@@ -94,8 +94,8 @@ Feature: With clause
       RETURN x.c
       """
     Then the result should be, in any order:
-      | x.c          |
-      | UNKNOWN_PROP |
+      | x.c      |
+      | __NULL__ |
 
   Scenario: match with return
     When executing query:
diff --git a/tests/tck/features/optimizer/PrunePropertiesRule.feature b/tests/tck/features/optimizer/PrunePropertiesRule.feature
index 5429bf2fb82..856301020e9 100644
--- a/tests/tck/features/optimizer/PrunePropertiesRule.feature
+++ b/tests/tck/features/optimizer/PrunePropertiesRule.feature
@@ -747,9 +747,9 @@ Feature: Prune Properties rule
       """
     Then the result should be, in order, with relax comparison:
       | properties(src_v).age | properties(e).degree | name              | src_v.player.sex | e.start_year | dst_v.player.age |
-      | 41                    | UNKNOWN_PROP         | "Dejounte Murray" | "男"             | 2022         | 29               |
+      | 41                    | __NULL__             | "Dejounte Murray" | "男"             | 2022         | 29               |
       | 41                    | 88                   | "Spurs"           | "男"             | 2002         | NULL             |
-      | 41                    | UNKNOWN_PROP         | "Tiago Splitter"  | "男"             | 2022         | 34               |
+      | 41                    | __NULL__             | "Tiago Splitter"  | "男"             | 2022         | 34               |
     When executing query:
       """
       match (src_v:player{name:"Manu Ginobili"})-[e*2]-(dst_v)
@@ -759,10 +759,10 @@ Feature: Prune Properties rule
     Then the result should be, in order, with relax comparison:
       | properties(src_v).sex | properties(e[0]).degree | properties(dst_v).name | age | e[1].start_year | dst_v.player.age |
       | "男"                  | 88                      | "Danny Green"          | 41  | 2010            | 31               |
-      | "男"                  | UNKNOWN_PROP            | "Danny Green"          | 41  | 2022            | 31               |
-      | "男"                  | UNKNOWN_PROP            | "LeBron James"         | 41  | 2022            | 34               |
+      | "男"                  | __NULL__                | "Danny Green"          | 41  | 2022            | 31               |
+      | "男"                  | __NULL__                | "LeBron James"         | 41  | 2022            | 34               |
       | "男"                  | 88                      | "Cory Joseph"          | 41  | 2011            | 27               |
-      | "男"                  | UNKNOWN_PROP            | "76ers"                | 41  | 2017            | NULL             |
+      | "男"                  | __NULL__                | "76ers"                | 41  | 2017            | NULL             |
     When executing query:
       """
       match (src_v:player{name:"Manu Ginobili"})-[e:like*2..3]-(dst_v)
@@ -771,11 +771,11 @@ Feature: Prune Properties rule
       """
     Then the result should be, in order, with relax comparison:
       | properties(src_v).sex | properties(e[0]).degree | properties(dst_v).name | age | e[1].start_year | dst_v.player.age |
-      | "男"                  | UNKNOWN_PROP            | "Danny Green"          | 41  | 2022            | 31               |
-      | "男"                  | UNKNOWN_PROP            | "Danny Green"          | 41  | 2022            | 31               |
-      | "男"                  | UNKNOWN_PROP            | "Kyle Anderson"        | 41  | 2022            | 25               |
-      | "男"                  | UNKNOWN_PROP            | "LeBron James"         | 41  | 2022            | 34               |
-      | "男"                  | UNKNOWN_PROP            | "Kevin Durant"         | 41  | 2022            | 30               |
+      | "男"                  | __NULL__                | "Danny Green"          | 41  | 2022            | 31               |
+      | "男"                  | __NULL__                | "Danny Green"          | 41  | 2022            | 31               |
+      | "男"                  | __NULL__                | "Kyle Anderson"        | 41  | 2022            | 25               |
+      | "男"                  | __NULL__                | "LeBron James"         | 41  | 2022            | 34               |
+      | "男"                  | __NULL__                | "Kevin Durant"         | 41  | 2022            | 30               |
     When executing query:
       """
       match (v1)-->(v2)-->(v3) where id(v1)=="Manu Ginobili"
@@ -841,9 +841,9 @@ Feature: Prune Properties rule
     Then the result should be, in order, with relax comparison:
       | properties(e).degree | degree |
       | 88                   | 88     |
-      | UNKNOWN_PROP         | 88     |
+      | __NULL__             | 88     |
       | 88                   | 88     |
-      | UNKNOWN_PROP         | 88     |
+      | __NULL__             | 88     |
       | 88                   | 88     |
     When executing query:
       """
@@ -851,9 +851,9 @@ Feature: Prune Properties rule
       """
     Then the result should be, in order, with relax comparison:
       | properties(e).degree1 | properties(e).degree1 | e2.a | dst_v.p.name | dst_v.player.sex1 | properties(src_v).name2 |
-      | UNKNOWN_PROP          | UNKNOWN_PROP          | NULL | NULL         | NULL              | UNKNOWN_PROP            |
-      | UNKNOWN_PROP          | UNKNOWN_PROP          | NULL | NULL         | NULL              | UNKNOWN_PROP            |
-      | UNKNOWN_PROP          | UNKNOWN_PROP          | NULL | NULL         | NULL              | UNKNOWN_PROP            |
-      | UNKNOWN_PROP          | UNKNOWN_PROP          | NULL | NULL         | NULL              | UNKNOWN_PROP            |
-      | UNKNOWN_PROP          | UNKNOWN_PROP          | NULL | NULL         | NULL              | UNKNOWN_PROP            |
+      | __NULL__              | __NULL__              | NULL | NULL         | NULL              | __NULL__                |
+      | __NULL__              | __NULL__              | NULL | NULL         | NULL              | __NULL__                |
+      | __NULL__              | __NULL__              | NULL | NULL         | NULL              | __NULL__                |
+      | __NULL__              | __NULL__              | NULL | NULL         | NULL              | __NULL__                |
+      | __NULL__              | __NULL__              | NULL | NULL         | NULL              | __NULL__                |
     Then drop the used space
diff --git a/tests/tck/features/parser/nebula.feature b/tests/tck/features/parser/nebula.feature
index 7e802ce4155..9d9fc4e09e1 100644
--- a/tests/tck/features/parser/nebula.feature
+++ b/tests/tck/features/parser/nebula.feature
@@ -17,7 +17,7 @@ Feature: Value parsing
       | BAD_DATA                                             | BAD_DATA     |
       | BAD_TYPE                                             | BAD_TYPE     |
       | OVERFLOW                                             | ERR_OVERFLOW |
-      | UNKNOWN_PROP                                         | UNKNOWN_PROP |
+      | __NULL__                                             | NULL         |
       | DIV_BY_ZERO                                          | DIV_BY_ZERO  |
       | OUT_OF_RANGE                                         | OUT_OF_RANGE |
       | 123                                                  | iVal         |
diff --git a/tests/tck/utils/nbv.py b/tests/tck/utils/nbv.py
index 6bc4e3a1714..fb75b0569ae 100644
--- a/tests/tck/utils/nbv.py
+++ b/tests/tck/utils/nbv.py
@@ -42,7 +42,7 @@
     'BAD_DATA',
     'BAD_TYPE',
     'OVERFLOW',
-    'UNKNOWN_PROP',
+    '__NULL__',
     'DIV_BY_ZERO',
     'OUT_OF_RANGE',
     'FLOAT',
@@ -100,9 +100,9 @@ def t_OVERFLOW(t):
     return t
 
 
-def t_UNKNOWN_PROP(t):
-    r'UNKNOWN_PROP'
-    t.value = Value(nVal=NullType.UNKNOWN_PROP)
+def t___NULL__(t):
+    r'__NULL__'
+    t.value = Value(nVal=NullType.__NULL__)
     return t
 
 
@@ -239,7 +239,7 @@ def p_expr(p):
              | BAD_DATA
              | BAD_TYPE
              | OVERFLOW
-             | UNKNOWN_PROP
+             | __NULL__
              | DIV_BY_ZERO
              | OUT_OF_RANGE
              | INT
@@ -587,7 +587,7 @@ def parse_row(row):
     expected['BAD_DATA'] = Value(nVal=NullType.BAD_DATA)
     expected['BAD_TYPE'] = Value(nVal=NullType.BAD_TYPE)
     expected['OVERFLOW'] = Value(nVal=NullType.ERR_OVERFLOW)
-    expected['UNKNOWN_PROP'] = Value(nVal=NullType.UNKNOWN_PROP)
+    expected['__NULL__'] = Value(nVal=NullType.__NULL__)
     expected['DIV_BY_ZERO'] = Value(nVal=NullType.DIV_BY_ZERO)
     expected['OUT_OF_RANGE'] = Value(nVal=NullType.OUT_OF_RANGE)
     expected['123'] = Value(iVal=123)