diff --git a/unmaintained/diff_volume_servers/diff_volume_servers.go b/unmaintained/diff_volume_servers/diff_volume_servers.go
index 6107f3d48..137cb82cf 100644
--- a/unmaintained/diff_volume_servers/diff_volume_servers.go
+++ b/unmaintained/diff_volume_servers/diff_volume_servers.go
@@ -158,6 +158,9 @@ func getVolumeFiles(v uint32, addr string) (map[types.NeedleId]needleState, int6
 	files := map[types.NeedleId]needleState{}
 	err = idx.WalkIndexFile(idxFile, func(key types.NeedleId, offset types.Offset, size types.Size) error {
 		if offset.IsZero() || size.IsDeleted() {
+			if size < 0 {
+				size = -size
+			}
 			files[key] = needleState{
 				state: stateDeleted,
 				size:  size,