diff --git a/source/libs/function/src/udfd.c b/source/libs/function/src/udfd.c
index 61c6f92e2f8daff3735168e3ed92c3fd600a28c5..5034af2f8264dab3312950369c15d4fb890b38b7 100644
--- a/source/libs/function/src/udfd.c
+++ b/source/libs/function/src/udfd.c
@@ -688,6 +688,8 @@ void udfdProcessCallRequest(SUvUdfWork *uvUdf, SUdfRequest *request) {
       output.colMeta.type = udf->outputType;
       output.colMeta.precision = 0;
       output.colMeta.scale = 0;
+      udfColEnsureCapacity(&output, call->block.info.rows);
+
       SUdfDataBlock input = {0};
       convertDataBlockToUdfDataBlock(&call->block, &input);
       code = udf->scriptPlugin->udfScalarProcFunc(&input, &output, udf->scriptUdfCtx);