diff --git a/consensus/ibft/src/main/java/tech/pegasys/pantheon/consensus/ibft/UniqueMessageMulticaster.java b/consensus/ibft/src/main/java/tech/pegasys/pantheon/consensus/ibft/UniqueMessageMulticaster.java
index dc6dc3bbae..4e76648df3 100644
--- a/consensus/ibft/src/main/java/tech/pegasys/pantheon/consensus/ibft/UniqueMessageMulticaster.java
+++ b/consensus/ibft/src/main/java/tech/pegasys/pantheon/consensus/ibft/UniqueMessageMulticaster.java
@@ -14,6 +14,7 @@ package tech.pegasys.pantheon.consensus.ibft;
 
 import tech.pegasys.pantheon.consensus.ibft.network.ValidatorMulticaster;
 import tech.pegasys.pantheon.ethereum.core.Address;
+import tech.pegasys.pantheon.ethereum.core.Hash;
 import tech.pegasys.pantheon.ethereum.p2p.api.MessageData;
 
 import java.util.Collection;
@@ -42,11 +43,11 @@ public class UniqueMessageMulticaster implements ValidatorMulticaster {
   }
 
   // Set that starts evicting members when it hits capacity
-  private final Set<Integer> seenMessages =
+  private final Set<Hash> seenMessages =
       Collections.newSetFromMap(
-          new LinkedHashMap<Integer, Boolean>() {
+          new LinkedHashMap<Hash, Boolean>() {
             @Override
-            protected boolean removeEldestEntry(final Map.Entry<Integer, Boolean> eldest) {
+            protected boolean removeEldestEntry(final Map.Entry<Hash, Boolean> eldest) {
               return size() > maxSeenMessages;
             }
           });
@@ -58,7 +59,7 @@ public class UniqueMessageMulticaster implements ValidatorMulticaster {
 
   @Override
   public void send(final MessageData message, final Collection<Address> blackList) {
-    final int uniqueID = message.hashCode();
+    final Hash uniqueID = Hash.hash(message.getData());
     if (seenMessages.contains(uniqueID)) {
       return;
     }
diff --git a/consensus/ibft/src/test/java/tech/pegasys/pantheon/consensus/ibft/UniqueMessageMulticasterTest.java b/consensus/ibft/src/test/java/tech/pegasys/pantheon/consensus/ibft/UniqueMessageMulticasterTest.java
index a832780423..51931ef46b 100644
--- a/consensus/ibft/src/test/java/tech/pegasys/pantheon/consensus/ibft/UniqueMessageMulticasterTest.java
+++ b/consensus/ibft/src/test/java/tech/pegasys/pantheon/consensus/ibft/UniqueMessageMulticasterTest.java
@@ -85,9 +85,46 @@ public class UniqueMessageMulticasterTest {
 
   @Test
   public void passedInBlackListIsPassedToUnderlyingValidator() {
-    List<Address> blackList =
+    final List<Address> blackList =
         Lists.newArrayList(AddressHelpers.ofValue(0), AddressHelpers.ofValue(1));
     messageTracker.send(messageSent, blackList);
     verify(multicaster, times(1)).send(messageSent, blackList);
   }
+
+  @Test
+  public void anonymousMessageDataClassesContainingTheSameDataAreConsideredIdentical() {
+
+    final MessageData arbitraryMessage_1 =
+        createAnonymousMessageData(BytesValue.wrap(new byte[4]), 1);
+
+    final MessageData arbitraryMessage_2 =
+        createAnonymousMessageData(BytesValue.wrap(new byte[4]), 1);
+
+    messageTracker.send(arbitraryMessage_1);
+    verify(multicaster, times(1)).send(arbitraryMessage_1, emptyList());
+    reset(multicaster);
+
+    messageTracker.send(arbitraryMessage_2);
+    verifyZeroInteractions(multicaster);
+  }
+
+  private MessageData createAnonymousMessageData(final BytesValue content, final int code) {
+    return new MessageData() {
+
+      @Override
+      public int getSize() {
+        return content.size();
+      }
+
+      @Override
+      public int getCode() {
+        return code;
+      }
+
+      @Override
+      public BytesValue getData() {
+        return content;
+      }
+    };
+  }
 }