diff --git a/drools-core/src/main/java/org/drools/core/phreak/PhreakAccumulateNode.java b/drools-core/src/main/java/org/drools/core/phreak/PhreakAccumulateNode.java
index 82f452b1672..a85b117d5f7 100644
--- a/drools-core/src/main/java/org/drools/core/phreak/PhreakAccumulateNode.java
+++ b/drools-core/src/main/java/org/drools/core/phreak/PhreakAccumulateNode.java
@@ -19,6 +19,7 @@
 import org.drools.core.rule.ContextEntry;
 import org.drools.core.spi.AlphaNodeFieldConstraint;
 import org.drools.core.spi.PropagationContext;
+import org.drools.core.util.AbstractHashTable;
 import org.drools.core.util.FastIterator;
 
 /**
@@ -120,11 +121,15 @@ public void doLeftInserts(AccumulateNode accNode,
         ContextEntry[] contextEntry = bm.getContext();
         BetaConstraints constraints = accNode.getRawConstraints();
 
+        boolean leftTupleMemoryEnabled = accNode.isLeftTupleMemoryEnabled();
+        if (leftTupleMemoryEnabled && srcLeftTuples.insertSize() > 32 && ltm instanceof AbstractHashTable) {
+            ((AbstractHashTable) ltm).ensureCapacity(srcLeftTuples.insertSize());
+        }
 
         for (LeftTuple leftTuple = srcLeftTuples.getInsertFirst(); leftTuple != null; ) {
             LeftTuple next = leftTuple.getStagedNext();
 
-            boolean useLeftMemory = RuleNetworkEvaluator.useLeftMemory(accNode, leftTuple);
+            boolean useLeftMemory = leftTupleMemoryEnabled || RuleNetworkEvaluator.useLeftMemory(accNode, leftTuple);
 
             if (useLeftMemory) {
                 ltm.add(leftTuple);
@@ -204,6 +209,10 @@ public void doRightInserts(AccumulateNode accNode,
         ContextEntry[] contextEntry = bm.getContext();
         BetaConstraints constraints = accNode.getRawConstraints();
 
+        if (srcRightTuples.insertSize() > 32 && rtm instanceof AbstractHashTable) {
+            ((AbstractHashTable) rtm).ensureCapacity(srcRightTuples.insertSize());
+        }
+
         for (RightTuple rightTuple = srcRightTuples.getInsertFirst(); rightTuple != null; ) {
             RightTuple next = rightTuple.getStagedNext();
 
diff --git a/drools-core/src/main/java/org/drools/core/util/AbstractHashTable.java b/drools-core/src/main/java/org/drools/core/util/AbstractHashTable.java
index 8f51e5dc5d8..9e78a4adf67 100644
--- a/drools-core/src/main/java/org/drools/core/util/AbstractHashTable.java
+++ b/drools-core/src/main/java/org/drools/core/util/AbstractHashTable.java
@@ -108,6 +108,17 @@ public void setComparator(final ObjectComparator comparator) {
         this.comparator = comparator;
     }
 
+    public void ensureCapacity(int itemsToBeAdded) {
+        int newCapacity = this.size + itemsToBeAdded;
+        if (newCapacity > this.threshold) {
+            int newSize = this.table.length * 2;
+            while (newSize < newCapacity) {
+                newSize *= 2;
+            }
+            resize(newSize);
+        }
+    }
+
     protected void resize(final int newCapacity) {
         final Entry[] oldTable = this.table;
         final int oldCapacity = oldTable.length;