diff --git a/spring-ai-rag/src/main/java/org/springframework/ai/rag/advisor/RetrievalAugmentationAdvisor.java b/spring-ai-rag/src/main/java/org/springframework/ai/rag/advisor/RetrievalAugmentationAdvisor.java
index 10cfea33584..b9e608be2b1 100644
--- a/spring-ai-rag/src/main/java/org/springframework/ai/rag/advisor/RetrievalAugmentationAdvisor.java
+++ b/spring-ai-rag/src/main/java/org/springframework/ai/rag/advisor/RetrievalAugmentationAdvisor.java
@@ -130,7 +130,7 @@ public ChatClientRequest before(ChatClientRequest chatClientRequest, @Nullable A
 			.toList()
 			.stream()
 			.map(CompletableFuture::join)
-			.collect(Collectors.toMap(Map.Entry::getKey, entry -> List.of(entry.getValue())));
+			.collect(Collectors.toMap(Map.Entry::getKey, entry -> List.of(entry.getValue()), (v1, v2) -> v2));
 
 		// 4. Combine documents retrieved based on multiple queries and from multiple data
 		// sources.