diff --git a/org.springframework.integration/src/main/java/org/springframework/integration/aggregator/CorrelatingMessageHandler.java b/org.springframework.integration/src/main/java/org/springframework/integration/aggregator/CorrelatingMessageHandler.java
index 1d583c1075..56a2732759 100644
--- a/org.springframework.integration/src/main/java/org/springframework/integration/aggregator/CorrelatingMessageHandler.java
+++ b/org.springframework.integration/src/main/java/org/springframework/integration/aggregator/CorrelatingMessageHandler.java
@@ -318,7 +318,7 @@ public class CorrelatingMessageHandler extends AbstractMessageHandler implements
 							}
 							for (Message<?> message : all) {
 								discardChannel.send(message);
-								store.delete(message.getHeaders().getId());
+								store.delete(key, message.getHeaders().getId());
 							}
 						}
 					}
diff --git a/org.springframework.integration/src/main/java/org/springframework/integration/store/SimpleMessageStore.java b/org.springframework.integration/src/main/java/org/springframework/integration/store/SimpleMessageStore.java
index b13f759693..d43b989627 100644
--- a/org.springframework.integration/src/main/java/org/springframework/integration/store/SimpleMessageStore.java
+++ b/org.springframework.integration/src/main/java/org/springframework/integration/store/SimpleMessageStore.java
@@ -98,7 +98,7 @@ public class SimpleMessageStore implements MessageStore {
 		if (collection==null) {
 			return Collections.emptySet();
 		}
-		return Collections.unmodifiableCollection(collection);
+		return new HashSet<Message<?>>(collection);
 	}
 
 	public void put(Object correlationId, Collection<Message<?>> messages) {