diff --git a/cpp/core/config/GlutenConfig.h b/cpp/core/config/GlutenConfig.h
index a039537b78ba..ad7dacf113ec 100644
--- a/cpp/core/config/GlutenConfig.h
+++ b/cpp/core/config/GlutenConfig.h
@@ -30,8 +30,6 @@ const std::string kGlutenSaveDir = "spark.gluten.saveDir";
 
 const std::string kCaseSensitive = "spark.sql.caseSensitive";
 
-const std::string kLegacySize = "spark.sql.legacy.sizeOfNull";
-
 const std::string kSessionTimezone = "spark.sql.session.timeZone";
 
 const std::string kIgnoreMissingFiles = "spark.sql.files.ignoreMissingFiles";
diff --git a/cpp/velox/compute/WholeStageResultIterator.cc b/cpp/velox/compute/WholeStageResultIterator.cc
index cbc6c838b1b7..296b9415b159 100644
--- a/cpp/velox/compute/WholeStageResultIterator.cc
+++ b/cpp/velox/compute/WholeStageResultIterator.cc
@@ -454,8 +454,6 @@ std::unordered_map<std::string, std::string> WholeStageResultIterator::getQueryC
     }
     // Adjust timestamp according to the above configured session timezone.
     configs[velox::core::QueryConfig::kAdjustTimestampToTimezone] = "true";
-    // Align Velox size function with Spark.
-    configs[velox::core::QueryConfig::kSparkLegacySizeOfNull] = std::to_string(veloxCfg_->get<bool>(kLegacySize, true));
 
     {
       // partial aggregation memory config