diff --git a/src/sql/ob_spi.cpp b/src/sql/ob_spi.cpp
index f8a7dc17e..7510d227d 100644
--- a/src/sql/ob_spi.cpp
+++ b/src/sql/ob_spi.cpp
@@ -5980,6 +5980,9 @@ int ObSPIService::convert_obj(ObPLExecCtx *ctx,
   for (int i = 0; OB_SUCC(ret) && i < obj_array.count(); ++i) {
     ObObj &obj = obj_array.at(i);
     tmp_obj.reset();
+    if (obj.is_clob()) {
+      obj.set_collation_type(result_types[i].get_collation_type());
+    }
     obj.set_collation_level(result_types[i].get_collation_level());
     LOG_DEBUG("column convert", K(obj.get_meta()), K(result_types[i].get_meta_type()),
               K(current_type.at(i)), K(result_types[i].get_accuracy()));