diff --git a/src/Consumer/Assignor/RangeAssignor.php b/src/Consumer/Assignor/RangeAssignor.php
index 942f7dc..3114c07 100644
--- a/src/Consumer/Assignor/RangeAssignor.php
+++ b/src/Consumer/Assignor/RangeAssignor.php
@@ -64,7 +64,7 @@ public function assign(array $topicMetadatas, array $groupMembers): array
                 /** @var ConsumerGroupMemberAssignment $consumerGroupMemberAssignment */
                 $consumerGroupMemberAssignment = $topicMembers[$topicName][$memberIds[$i]]['assignment'];
                 $consumerGroupTopic = new ConsumerGroupTopic();
-                $consumerGroupTopic->setTopicName($topicName);
+                $consumerGroupTopic->setTopicName((string) $topicName);
                 $consumerGroupTopic->setPartitions(\array_slice($topicPartitions, $start, $length));
                 $topics = $consumerGroupMemberAssignment->getTopics();
                 $topics[] = $consumerGroupTopic;