diff --git a/spring-integration-core/src/main/java/org/springframework/integration/aggregator/AbstractCorrelatingMessageHandler.java b/spring-integration-core/src/main/java/org/springframework/integration/aggregator/AbstractCorrelatingMessageHandler.java
index bc7ef3ae94..fb002fe735 100644
--- a/spring-integration-core/src/main/java/org/springframework/integration/aggregator/AbstractCorrelatingMessageHandler.java
+++ b/spring-integration-core/src/main/java/org/springframework/integration/aggregator/AbstractCorrelatingMessageHandler.java
@@ -147,7 +147,7 @@ public abstract class AbstractCorrelatingMessageHandler extends AbstractMessageH
 	}
 
 	public AbstractCorrelatingMessageHandler(MessageGroupProcessor processor) {
-		this(processor, SimpleMessageStore.fastMessageStore(0), null, null);
+		this(processor, new SimpleMessageStore(0), null, null);
 	}
 
 	public void setLockRegistry(LockRegistry lockRegistry) {
diff --git a/spring-integration-core/src/main/java/org/springframework/integration/store/SimpleMessageStore.java b/spring-integration-core/src/main/java/org/springframework/integration/store/SimpleMessageStore.java
index 433a0f750d..f6a8158e1a 100644
--- a/spring-integration-core/src/main/java/org/springframework/integration/store/SimpleMessageStore.java
+++ b/spring-integration-core/src/main/java/org/springframework/integration/store/SimpleMessageStore.java
@@ -57,7 +57,7 @@ public class SimpleMessageStore extends AbstractMessageGroupStore
 
 	private volatile boolean isUsed;
 
-	private volatile boolean copyOnGet = true; // TODO: default false in 4.1
+	private volatile boolean copyOnGet = false;
 
 	/**
 	 * Creates a SimpleMessageStore with a maximum size limited by the given capacity, or unlimited size if the given
@@ -113,7 +113,9 @@ public class SimpleMessageStore extends AbstractMessageGroupStore
 	 * @param capacity the capacity (0 for unlimited).
 	 * @return the store.
 	 * @since 4.0.1
+	 * @deprecated in 4.1 - copyOnGet is now false by default.
 	 */
+	@Deprecated
 	public static SimpleMessageStore fastMessageStore(int capacity) {
 		SimpleMessageStore store = new SimpleMessageStore(capacity);
 		store.setCopyOnGet(false);
@@ -122,6 +124,7 @@ public class SimpleMessageStore extends AbstractMessageGroupStore
 
 	/**
 	 * Set to false to disable copying the group in {@link #getMessageGroup(Object)}.
+	 * Starting with 4.1, this is false by default.
 	 * @param copyOnGet True to copy, false to not.
 	 * @since 4.0.1
 	 */
diff --git a/src/reference/docbook/message-store.xml b/src/reference/docbook/message-store.xml
index 8f946fda88..f8a2e6a9ff 100644
--- a/src/reference/docbook/message-store.xml
+++ b/src/reference/docbook/message-store.xml
@@ -107,4 +107,22 @@
 		</itemizedlist>
 	</para>
 
+	<caution id="sms-caution">
+		<title>Caution with SimpleMessageStore</title>
+		<para>
+			Starting with <emphasis>version 4.1</emphasis>, the <classname>SimpleMessageStore</classname> no longer copies
+			the message group when calling <code>getMessageGroup()</code>. For large message groups, this was a significant
+			performance problem. 4.0.1 introduced a boolean <code>copyOnGet</code> allowing this to be controlled. When
+			used internally by the aggregator, this was set to false to improve performance. It is now false by default.
+		</para>
+		<para>
+			Users accessing the group store outside of components such as aggregators, will now get a direct reference
+			to the group being used by the aggregator, instead of a copy. Manipulation of the group outside of the aggregator may
+			cause unpredictable results.
+		</para>
+		<para>
+			For this reason, users should not perform such manipulation, or set the <code>copyOnGet</code>
+			property to <code>true</code>.
+		</para>
+	</caution>
 </section>
diff --git a/src/reference/docbook/whats-new.xml b/src/reference/docbook/whats-new.xml
index 27b926935b..3621d4d8f1 100644
--- a/src/reference/docbook/whats-new.xml
+++ b/src/reference/docbook/whats-new.xml
@@ -11,7 +11,7 @@
 	</para>
 	<section id="4.1-general">
 		<title>General Changes</title>
-		<section>
+		<section id="4.1-amqp-outbound-lazy-connect">
 			<title>AMQP Outbound Endpoints</title>
 			<para>
 				The AMQP outbound endpoints support a new property <code>lazy-connect</code>
@@ -22,5 +22,13 @@
 				See <xref linkend="amqp"/> for more information.
 			</para>
 		</section>
+		<section id="4.1-sms-copy-on-get">
+			<title>SimpleMessageStore</title>
+			<para>
+				The <classname>SimpleMessageStore</classname> no longer makes a copy of the group
+				when calling <code>getMessageGroup()</code>.
+				See <xref linkend="sms-caution"/> for more information.
+			</para>
+		</section>
 	</section>
 </chapter>