diff --git a/arbnode/inbox_reader.go b/arbnode/inbox_reader.go
index 0e9a33f4fd..34fec275e5 100644
--- a/arbnode/inbox_reader.go
+++ b/arbnode/inbox_reader.go
@@ -665,7 +665,7 @@ func (r *InboxReader) getNextBlockToRead(ctx context.Context) (*big.Int, error)
 	if delayedCount == 0 {
 		return new(big.Int).Set(r.firstMessageBlock), nil
 	}
-	_, _, parentChainBlockNumber, err := r.tracker.GetDelayedMessageAccumulatorAndParentChainBlockNumber(ctx, delayedCount-1)
+	parentChainBlockNumber, err := r.tracker.GetParentChainBlockNumberFor(ctx, delayedCount-1)
 	if err != nil {
 		return nil, err
 	}
diff --git a/arbnode/inbox_tracker.go b/arbnode/inbox_tracker.go
index 7aa56b7db2..5c742b1947 100644
--- a/arbnode/inbox_tracker.go
+++ b/arbnode/inbox_tracker.go
@@ -347,6 +347,25 @@ func (t *InboxTracker) legacyGetDelayedMessageAndAccumulator(ctx context.Context
 }
 
 func (t *InboxTracker) GetDelayedMessageAccumulatorAndParentChainBlockNumber(ctx context.Context, seqNum uint64) (*arbostypes.L1IncomingMessage, common.Hash, uint64, error) {
+	msg, acc, blockNum, err := t.getRawDelayedMessageAccumulatorAndParentChainBlockNumber(ctx, seqNum)
+	if err != nil {
+		return msg, acc, blockNum, err
+	}
+	err = msg.FillInBatchGasFields(func(batchNum uint64) ([]byte, error) {
+		data, _, err := t.txStreamer.inboxReader.GetSequencerMessageBytes(ctx, batchNum)
+		return data, err
+	})
+	return msg, acc, blockNum, err
+}
+
+// does not return message, so does not need to fill in batchGasFields
+func (t *InboxTracker) GetParentChainBlockNumberFor(ctx context.Context, seqNum uint64) (uint64, error) {
+	_, _, blockNum, err := t.getRawDelayedMessageAccumulatorAndParentChainBlockNumber(ctx, seqNum)
+	return blockNum, err
+}
+
+// this function will not error
+func (t *InboxTracker) getRawDelayedMessageAccumulatorAndParentChainBlockNumber(ctx context.Context, seqNum uint64) (*arbostypes.L1IncomingMessage, common.Hash, uint64, error) {
 	delayedMessageKey := dbKey(rlpDelayedMessagePrefix, seqNum)
 	exists, err := t.db.Has(delayedMessageKey)
 	if err != nil {
@@ -371,14 +390,6 @@ func (t *InboxTracker) GetDelayedMessageAccumulatorAndParentChainBlockNumber(ctx
 		return msg, acc, 0, err
 	}
 
-	err = msg.FillInBatchGasFields(func(batchNum uint64) ([]byte, error) {
-		data, _, err := t.txStreamer.inboxReader.GetSequencerMessageBytes(ctx, batchNum)
-		return data, err
-	})
-	if err != nil {
-		return msg, acc, 0, err
-	}
-
 	parentChainBlockNumberKey := dbKey(parentChainBlockNumberPrefix, seqNum)
 	exists, err = t.db.Has(parentChainBlockNumberKey)
 	if err != nil {