diff --git a/bramble-core/src/main/java/org/briarproject/bramble/sync/MessageFactoryImpl.java b/bramble-core/src/main/java/org/briarproject/bramble/sync/MessageFactoryImpl.java
index 7ca6824a3d2f6ecc0628dc1d392864c84bb341a1..e7a68d7d8a50d0328473b72bed38c9b92e341c2d 100644
--- a/bramble-core/src/main/java/org/briarproject/bramble/sync/MessageFactoryImpl.java
+++ b/bramble-core/src/main/java/org/briarproject/bramble/sync/MessageFactoryImpl.java
@@ -12,8 +12,10 @@ import org.briarproject.bramble.util.ByteUtils;
 import javax.annotation.concurrent.Immutable;
 import javax.inject.Inject;
 
+import static org.briarproject.bramble.api.sync.MessageId.LABEL;
 import static org.briarproject.bramble.api.sync.SyncConstants.MAX_MESSAGE_BODY_LENGTH;
 import static org.briarproject.bramble.api.sync.SyncConstants.MESSAGE_HEADER_LENGTH;
+import static org.briarproject.bramble.api.sync.SyncConstants.PROTOCOL_VERSION;
 
 @Immutable
 @NotNullByDefault
@@ -32,9 +34,9 @@ class MessageFactoryImpl implements MessageFactory {
 			throw new IllegalArgumentException();
 		byte[] timeBytes = new byte[ByteUtils.INT_64_BYTES];
 		ByteUtils.writeUint64(timestamp, timeBytes, 0);
-		byte[] idHash =
-				crypto.hash(MessageId.LABEL, g.getBytes(), timeBytes, body);
-		MessageId id = new MessageId(idHash);
+		byte[] hash = crypto.hash(LABEL, new byte[] {PROTOCOL_VERSION},
+				g.getBytes(), timeBytes, body);
+		MessageId id = new MessageId(hash);
 		byte[] raw = new byte[MESSAGE_HEADER_LENGTH + body.length];
 		System.arraycopy(g.getBytes(), 0, raw, 0, UniqueId.LENGTH);
 		ByteUtils.writeUint64(timestamp, raw, UniqueId.LENGTH);
diff --git a/briar-core/src/main/java/org/briarproject/briar/client/QueueMessageFactoryImpl.java b/briar-core/src/main/java/org/briarproject/briar/client/QueueMessageFactoryImpl.java
index 4dcc471ada1f6b79ef7b98081f98393f8a8cb38d..da8cb1426e996a2daa75c1503afce11c250e6baf 100644
--- a/briar-core/src/main/java/org/briarproject/briar/client/QueueMessageFactoryImpl.java
+++ b/briar-core/src/main/java/org/briarproject/briar/client/QueueMessageFactoryImpl.java
@@ -12,8 +12,10 @@ import org.briarproject.briar.api.client.QueueMessageFactory;
 import javax.annotation.concurrent.Immutable;
 import javax.inject.Inject;
 
+import static org.briarproject.bramble.api.sync.MessageId.LABEL;
 import static org.briarproject.bramble.api.sync.SyncConstants.MAX_MESSAGE_LENGTH;
 import static org.briarproject.bramble.api.sync.SyncConstants.MESSAGE_HEADER_LENGTH;
+import static org.briarproject.bramble.api.sync.SyncConstants.PROTOCOL_VERSION;
 import static org.briarproject.bramble.util.ByteUtils.INT_64_BYTES;
 import static org.briarproject.briar.api.client.QueueMessage.MAX_QUEUE_MESSAGE_BODY_LENGTH;
 import static org.briarproject.briar.api.client.QueueMessage.QUEUE_MESSAGE_HEADER_LENGTH;
@@ -45,9 +47,9 @@ class QueueMessageFactoryImpl implements QueueMessageFactory {
 		byte[] bodyBytes = new byte[body.length + INT_64_BYTES];
 		System.arraycopy(raw, MESSAGE_HEADER_LENGTH, bodyBytes, 0,
 				body.length + INT_64_BYTES);
-		MessageId id = new MessageId(
-				crypto.hash(MessageId.LABEL, groupId.getBytes(), timeBytes,
-						bodyBytes));
+		byte[] hash = crypto.hash(LABEL, new byte[] {PROTOCOL_VERSION},
+				groupId.getBytes(), timeBytes, bodyBytes);
+		MessageId id = new MessageId(hash);
 		return new QueueMessage(id, groupId, timestamp, queuePosition, raw);
 	}