From 88eb7894de6d567f80bca53fb8ba23b0f95cae8f Mon Sep 17 00:00:00 2001
From: Artem Bilan <abilan@pivotal.io>
Date: Fri, 11 Dec 2015 17:48:52 -0500
Subject: [PATCH] INT-3908: Fix NPE in the AbstractAggrMGProcessor

JIRA: https://jira.spring.io/browse/INT-3908

**Cherry-pick to ALL**
---
 .../AbstractAggregatingMessageGroupProcessor.java          | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/spring-integration-core/src/main/java/org/springframework/integration/aggregator/AbstractAggregatingMessageGroupProcessor.java b/spring-integration-core/src/main/java/org/springframework/integration/aggregator/AbstractAggregatingMessageGroupProcessor.java
index f863df4e33..9fb4e7675e 100644
--- a/spring-integration-core/src/main/java/org/springframework/integration/aggregator/AbstractAggregatingMessageGroupProcessor.java
+++ b/spring-integration-core/src/main/java/org/springframework/integration/aggregator/AbstractAggregatingMessageGroupProcessor.java
@@ -74,8 +74,11 @@ public abstract class AbstractAggregatingMessageGroupProcessor implements Messag
 				if (!aggregatedHeaders.containsKey(key)) {
 					aggregatedHeaders.put(key, value);
 				}
-				else if (!value.equals(aggregatedHeaders.get(key))) {
-					conflictKeys.add(key);
+				else {
+					Object existingValue = aggregatedHeaders.get(key);
+					if (value != existingValue && (value == null || !value.equals(existingValue))) {
+						conflictKeys.add(key);
+					}
 				}
 			}
 		}