diff --git a/contracts/javascore/aggregator/src/main/java/relay/aggregator/RelayAggregator.java b/contracts/javascore/aggregator/src/main/java/relay/aggregator/RelayAggregator.java
index 440b8c19..c597f81a 100644
--- a/contracts/javascore/aggregator/src/main/java/relay/aggregator/RelayAggregator.java
+++ b/contracts/javascore/aggregator/src/main/java/relay/aggregator/RelayAggregator.java
@@ -41,6 +41,7 @@ public class RelayAggregator {
     private final ArrayDB<Address> relayers = Context.newArrayDB("relayers", Address.class);
     private final DictDB<Address, Boolean> relayersLookup = Context.newDictDB("relayersLookup", Boolean.class);
 
+    private final DictDB<byte[], Boolean> acknowledgedPackets = Context.newDictDB("acknowledgedPackets", Boolean.class);
     private final DictDB<byte[], Packet> packets = Context.newDictDB("packets", Packet.class);
 
     private final BranchDB<byte[], DictDB<Address, byte[]>> signatures = Context.newBranchDB("signatures",
@@ -130,6 +131,20 @@ public boolean packetSubmitted(
         return existingSign != null;
     }
 
+    @External(readonly = true)
+    public boolean packetAcknowledged(
+            String srcNetwork,
+            String srcContractAddress,
+            BigInteger srcSn,
+            BigInteger srcHeight,
+            String dstNetwork,
+            String dstContractAddress,
+            byte[] data) {
+        Packet pkt = new Packet(srcNetwork, srcContractAddress, srcSn, srcHeight, dstNetwork, dstContractAddress, data);
+        byte[] pktID = pkt.getId();
+        return acknowledgedPackets.get(pktID) != null && acknowledgedPackets.get(pktID) == true;
+    }
+
     @External
     public void submitPacket(
             String srcNetwork,
@@ -146,6 +161,10 @@ public void submitPacket(
         Packet pkt = new Packet(srcNetwork, srcContractAddress, srcSn, srcHeight, dstNetwork, dstContractAddress, data);
         byte[] pktID = pkt.getId();
 
+        if (acknowledgedPackets.get(pktID) != null && acknowledgedPackets.get(pktID) == true) {
+            return;
+        }
+
         if (packets.get(pktID) == null) {
             packets.set(pktID, pkt);
             if (signatureThreshold.get() > 1) {
@@ -178,6 +197,7 @@ public void submitPacket(
                     pkt.getDstContractAddress(),
                     pkt.getData(),
                     encodedSigs);
+            acknowledgedPackets.set(pktID, true);
             removePacket(pktID);
         }
     }
diff --git a/contracts/javascore/aggregator/src/test/java/relay/aggregator/RelayAggregatorTest.java b/contracts/javascore/aggregator/src/test/java/relay/aggregator/RelayAggregatorTest.java
index 4165d4e6..9f1137d1 100644
--- a/contracts/javascore/aggregator/src/test/java/relay/aggregator/RelayAggregatorTest.java
+++ b/contracts/javascore/aggregator/src/test/java/relay/aggregator/RelayAggregatorTest.java
@@ -236,7 +236,7 @@ public void testPacketSubmitted_false() throws Exception {
         }
 
         @Test
-        public void testSubmitPacket() throws Exception {
+        public void testPacketAcknowledged_true() throws Exception {
                 String srcNetwork = "0x2.icon";
                 String dstNetwork = "sui";
                 BigInteger srcSn = BigInteger.ONE;
@@ -248,20 +248,40 @@ public void testSubmitPacket() throws Exception {
                 aggregator.invoke(adminAc, "setSignatureThreshold", 2);
 
                 byte[] dataHash = Context.hash("sha-256", data);
-                byte[] sign = relayerOne.sign(dataHash);
 
+                byte[] signOne = relayerOne.sign(dataHash);
                 aggregator.invoke(relayerOneAc, "submitPacket", srcNetwork,
                                 srcContractAddress, srcSn, srcHeight, dstNetwork,
+                                dstContractAddress,
+                                data,
+                                signOne);
+
+                byte[] signTwo = relayerTwo.sign(dataHash);
+                aggregator.invoke(relayerTwoAc, "submitPacket", srcNetwork,
+                                srcContractAddress, srcSn, srcHeight, dstNetwork,
+                                dstContractAddress,
+                                data,
+                                signTwo);
+
+                byte[][] sigs = new byte[2][];
+                sigs[0] = signOne;
+                sigs[1] = signTwo;
+
+                byte[] encodedSigs = RelayAggregator.serializeSignatures(sigs);
+                byte[][] decodedSigs = RelayAggregator.deserializeSignatures(encodedSigs);
+
+                assertArrayEquals(signOne, decodedSigs[0]);
+                assertArrayEquals(signTwo, decodedSigs[1]);
+
+                verify(aggregatorSpy).PacketAcknowledged(srcNetwork, srcContractAddress,
+                                srcSn, srcHeight, dstNetwork,
                                 dstContractAddress, data,
-                                sign);
+                                encodedSigs);
 
-                Packet pkt = new Packet(srcNetwork, srcContractAddress, srcSn, srcHeight, dstNetwork,
-                                dstContractAddress, data);
-                byte[] pktID = pkt.getId();
-                verify(aggregatorSpy).PacketRegistered(srcNetwork, srcContractAddress, srcSn,
-                                srcHeight, dstNetwork,
-                                dstContractAddress, data);
-                verify(aggregatorSpy).setSignature(pktID, relayerOneAc.getAddress(), sign);
+                boolean acknowledged = (boolean) aggregator.call("packetAcknowledged",
+                                srcNetwork,
+                                srcContractAddress, srcSn, srcHeight, dstNetwork, dstContractAddress, data);
+                assertEquals(acknowledged, true);
         }
 
         @Test