diff --git a/source/libs/scalar/src/sclfunc.c b/source/libs/scalar/src/sclfunc.c
index 5fa8eb0c9a..0161323e37 100644
--- a/source/libs/scalar/src/sclfunc.c
+++ b/source/libs/scalar/src/sclfunc.c
@@ -822,7 +822,7 @@ int32_t castFunction(SScalarParam *pInput, int32_t inputNum, SScalarParam *pOutp
           varDataSetLen(output, len);
         }
         //for constant conversion, need to set proper length of pOutput description
-        if (len < outputLen - VARSTR_HEADER_SIZE) {
+        if (len < outputLen) {
           pOutput->columnData->info.bytes = len;
         }
         break;