diff --git a/modAionImpl/src/org/aion/zero/impl/sync/SyncMgr.java b/modAionImpl/src/org/aion/zero/impl/sync/SyncMgr.java
index 079dbb870c..d34f675970 100644
--- a/modAionImpl/src/org/aion/zero/impl/sync/SyncMgr.java
+++ b/modAionImpl/src/org/aion/zero/impl/sync/SyncMgr.java
@@ -413,8 +413,11 @@ private void processImportBlocks() {
 
                     b = importedBlocks.take();
                     blockNumberIndex = b.getNumber();
-                    if (!savedHashes.containsKey(ByteArrayWrapper.wrap(b.getHash())))
+                    ByteArrayWrapper hash = new ByteArrayWrapper(b.getHash());
+                    if (!savedHashes.containsKey(hash)) {
                         batch.add(b);
+                        savedHashes.put(hash, null);
+                    }
                 }
 
                 // sleep if no batch empty then continue
@@ -423,6 +426,8 @@ private void processImportBlocks() {
                     continue;
                 }
 
+
+
                 boolean fetchAheadTriggerUsed = false;
 
                 for (AionBlock b : batch) {