diff --git a/index/scorch/snapshot_index.go b/index/scorch/snapshot_index.go
index 251aa9fa..800d250f 100644
--- a/index/scorch/snapshot_index.go
+++ b/index/scorch/snapshot_index.go
@@ -413,12 +413,10 @@ func docNumberToBytes(buf []byte, in uint64) []byte {
 }
 
 func docInternalToNumber(in index.IndexInternalID) (uint64, error) {
-	var res uint64
-	err := binary.Read(bytes.NewReader(in), binary.BigEndian, &res)
-	if err != nil {
-		return 0, err
+	if len(in) != 8 {
+		return 0, fmt.Errorf("wrong len for IndexInternalID: %q", in)
 	}
-	return res, nil
+	return binary.BigEndian.Uint64(in), nil
 }
 
 func (i *IndexSnapshot) DocumentVisitFieldTerms(id index.IndexInternalID,