diff --git a/src/client/src/tscSQLParser.c b/src/client/src/tscSQLParser.c
index 5befd5f33a14952a6835d5a92212dc4d3be435a6..627fb240c3ece6b821f99a5ad9858f787bd93596 100644
--- a/src/client/src/tscSQLParser.c
+++ b/src/client/src/tscSQLParser.c
@@ -4731,7 +4731,7 @@ static int32_t handleExprInQueryCond(SSqlCmd* pCmd, SQueryInfo* pQueryInfo, tSql
     if (pRight->tokenId == TK_NULL && (*pExpr)->tokenId == TK_EQ) {
       // transform for json->'key'=null
       pRight->tokenId = TK_STRING;
-      pRight->value.nType = TSDB_DATA_TYPE_BINARY;
+      pRight->value.nType = TSDB_DATA_TYPE_NCHAR;
       pRight->value.nLen = INT_BYTES;
       pRight->value.pz = calloc(INT_BYTES, 1);
       *(uint32_t*)pRight->value.pz = TSDB_DATA_JSON_null;