diff --git a/eth/downloader/downloader.go b/eth/downloader/downloader.go
index 3a177ab9de..b6f5760d9c 100644
--- a/eth/downloader/downloader.go
+++ b/eth/downloader/downloader.go
@@ -1488,7 +1488,11 @@ func (d *Downloader) importBlockResults(results []*fetchResult) error {
 		blocks[i] = types.NewBlockWithHeader(result.Header).WithBody(result.Transactions, result.Uncles)
 	}
 	if index, err := d.blockchain.InsertChain(blocks); err != nil {
-		log.Debug("Downloaded item processing failed", "number", results[index].Header.Number, "hash", results[index].Header.Hash(), "err", err)
+		if index < len(results) {
+			log.Debug("Downloaded item processing failed", "number", results[index].Header.Number, "hash", results[index].Header.Hash(), "err", err)
+		} else {
+			log.Debug("Downloaded item processing failed on sidechain import", "index", index, "err", err)
+		}
 		return errInvalidChain
 	}
 	return nil