diff --git a/modules/core/src/main/java/org/apache/synapse/mediators/eip/aggregator/Aggregate.java b/modules/core/src/main/java/org/apache/synapse/mediators/eip/aggregator/Aggregate.java
index cbd7998886..aa8acf2480 100755
--- a/modules/core/src/main/java/org/apache/synapse/mediators/eip/aggregator/Aggregate.java
+++ b/modules/core/src/main/java/org/apache/synapse/mediators/eip/aggregator/Aggregate.java
@@ -115,9 +115,6 @@ public Aggregate(SynapseEnvironment synEnv, String corelation, long timeoutMilli
      */
     public synchronized boolean addMessage(MessageContext synCtx) {
         if (maxCount <= 0 || (maxCount > 0 && messages.size() < maxCount)) {
-            if (messages == null) {
-                return false;
-            }
             messages.add(synCtx);
             return true;
         } else {
@@ -312,10 +309,14 @@ public void run() {
     }
 
     public synchronized boolean getLock() {
-        return !locked;
+        if (!locked) {
+            locked = true;
+            return true;
+        }
+        return false;
     }
 
-    public void releaseLock() {
+    public synchronized void releaseLock() {
         locked = false;
     }
 
diff --git a/modules/core/src/main/java/org/apache/synapse/mediators/v2/ScatterGather.java b/modules/core/src/main/java/org/apache/synapse/mediators/v2/ScatterGather.java
index 876183b7fe..c0e5e25f8f 100644
--- a/modules/core/src/main/java/org/apache/synapse/mediators/v2/ScatterGather.java
+++ b/modules/core/src/main/java/org/apache/synapse/mediators/v2/ScatterGather.java
@@ -448,7 +448,7 @@ private boolean aggregateMessages(MessageContext synCtx, SynapseLog synLog) {
             }
         } else {
             synLog.traceOrDebug("Unable to find aggregation correlation property");
-            return true;
+            return false;
         }
         // if there is an aggregate continue on aggregation
         if (aggregate != null) {
@@ -471,7 +471,6 @@ private boolean aggregateMessages(MessageContext synCtx, SynapseLog synLog) {
             }
         } else {
             synLog.traceOrDebug("Unable to find an aggregate for this message - skip");
-            return true;
         }
         return false;
     }