diff --git a/src/client/src/tscSQLParser.c b/src/client/src/tscSQLParser.c
index 7adc0812ae12bd8711cba5988806a4c7ba740cf5..6df724881e145a5698a73b228761dc68187465dd 100644
--- a/src/client/src/tscSQLParser.c
+++ b/src/client/src/tscSQLParser.c
@@ -4253,11 +4253,15 @@ static bool isValidExpr(tSqlExpr* pLeft, tSqlExpr* pRight, int32_t optr) {
   if (pRight == NULL) {
     return true;
   }
-  
+
   if (pLeft->tokenId >= TK_BOOL && pLeft->tokenId <= TK_BINARY && pRight->tokenId >= TK_BOOL && pRight->tokenId <= TK_BINARY) {
     return false;
   }
 
+  if (pLeft->tokenId >= TK_BOOL && pLeft->tokenId <= TK_BINARY && (optr == TK_NOTNULL || optr == TK_ISNULL)) {
+    return false;
+  }
+  
   return true;
 }