diff --git a/src/AggregationFunction/FunctionSum.php b/src/AggregationFunction/FunctionSum.php
index a5e800da..e344c3a2 100644
--- a/src/AggregationFunction/FunctionSum.php
+++ b/src/AggregationFunction/FunctionSum.php
@@ -69,7 +69,7 @@ public function processDataSource($dataSource): void
 				? $this->column
 				: current($dataSource->getRootAliases()) . '.' . $this->column;
 
-			$this->result = $dataSource
+			$this->result = (int) $dataSource
 				->select(sprintf('SUM(%s)', $column))
 				->setMaxResults(1)
 				->setFirstResult(0)