diff --git a/coordinator/src/main.rs b/coordinator/src/main.rs
index 04489680..19208cb3 100644
--- a/coordinator/src/main.rs
+++ b/coordinator/src/main.rs
@@ -600,7 +600,7 @@ pub async fn handle_processors<D: Db, Pro: Processors, P: P2p>(
             MainDb::<D>::save_first_preprocess(&mut txn, id.id, preprocess);
             txn.commit();
 
-            Some(Transaction::Batch(id.id))
+            Some(Transaction::Batch(block.0, id.id))
           } else {
             Some(Transaction::BatchPreprocess(SignData {
               plan: id.id,
diff --git a/coordinator/src/tests/tributary/mod.rs b/coordinator/src/tests/tributary/mod.rs
index 4ed87fd8..62ea82e7 100644
--- a/coordinator/src/tests/tributary/mod.rs
+++ b/coordinator/src/tests/tributary/mod.rs
@@ -103,9 +103,11 @@ fn serialize_transaction() {
   ));
 
   {
+    let mut block = [0; 32];
+    OsRng.fill_bytes(&mut block);
     let mut batch = [0; 32];
     OsRng.fill_bytes(&mut batch);
-    test_read_write(Transaction::Batch(batch));
+    test_read_write(Transaction::Batch(block, batch));
   }
   test_read_write(Transaction::SubstrateBlock(OsRng.next_u64()));
 
diff --git a/coordinator/src/tributary/handle.rs b/coordinator/src/tributary/handle.rs
index 7355b457..3c223867 100644
--- a/coordinator/src/tributary/handle.rs
+++ b/coordinator/src/tributary/handle.rs
@@ -443,7 +443,7 @@ pub async fn handle_application_tx<
       }
     }
 
-    Transaction::Batch(batch) => {
+    Transaction::Batch(_, batch) => {
       // Because this Batch has achieved synchrony, its batch ID should be authorized
       TributaryDb::<D>::recognize_id(txn, Zone::Batch.label(), genesis, batch);
       recognized_id(spec.set().network, genesis, RecognizedIdType::Batch, batch).await;
diff --git a/coordinator/src/tributary/mod.rs b/coordinator/src/tributary/mod.rs
index 3329b7e7..f7858ff0 100644
--- a/coordinator/src/tributary/mod.rs
+++ b/coordinator/src/tributary/mod.rs
@@ -232,7 +232,7 @@ pub enum Transaction {
   DkgConfirmed(u32, [u8; 32], Signed),
 
   // When we have synchrony on a batch, we can allow signing it
-  Batch([u8; 32]),
+  Batch([u8; 32], [u8; 32]),
   // When a Serai block is finalized, with the contained batches, we can allow the associated plan
   // IDs
   SubstrateBlock(u64),
@@ -331,9 +331,11 @@ impl ReadWrite for Transaction {
       }
 
       3 => {
+        let mut block = [0; 32];
+        reader.read_exact(&mut block)?;
         let mut batch = [0; 32];
         reader.read_exact(&mut batch)?;
-        Ok(Transaction::Batch(batch))
+        Ok(Transaction::Batch(block, batch))
       }
 
       4 => {
@@ -430,8 +432,9 @@ impl ReadWrite for Transaction {
         signed.write(writer)
       }
 
-      Transaction::Batch(batch) => {
+      Transaction::Batch(block, batch) => {
         writer.write_all(&[3])?;
+        writer.write_all(block)?;
         writer.write_all(batch)
       }
 
@@ -475,7 +478,7 @@ impl TransactionTrait for Transaction {
       Transaction::DkgShares { signed, .. } => TransactionKind::Signed(signed),
       Transaction::DkgConfirmed(_, _, signed) => TransactionKind::Signed(signed),
 
-      Transaction::Batch(_) => TransactionKind::Provided("batch"),
+      Transaction::Batch(_, _) => TransactionKind::Provided("batch"),
       Transaction::SubstrateBlock(_) => TransactionKind::Provided("serai"),
 
       Transaction::BatchPreprocess(data) => TransactionKind::Signed(&data.signed),
@@ -534,7 +537,7 @@ impl Transaction {
         Transaction::DkgShares { ref mut signed, .. } => signed,
         Transaction::DkgConfirmed(_, _, ref mut signed) => signed,
 
-        Transaction::Batch(_) => panic!("signing Batch"),
+        Transaction::Batch(_, _) => panic!("signing Batch"),
         Transaction::SubstrateBlock(_) => panic!("signing SubstrateBlock"),
 
         Transaction::BatchPreprocess(ref mut data) => &mut data.signed,