diff --git a/internal/repository/index.go b/internal/repository/index.go
index fd7ac1b94..6676d0635 100644
--- a/internal/repository/index.go
+++ b/internal/repository/index.go
@@ -46,8 +46,6 @@ type Index struct {
 	byType     [restic.NumBlobTypes]indexMap
 	packs      restic.IDs
 	mixedPacks restic.IDSet
-	// only used by Store, StorePacks does not check for already saved packIDs
-	packIDToIndex map[restic.ID]int
 
 	final      bool       // set to true for all indexes read from the backend ("finalized")
 	ids        restic.IDs // set to the IDs of the contained finalized indexes
@@ -58,9 +56,8 @@ type Index struct {
 // NewIndex returns a new index.
 func NewIndex() *Index {
 	return &Index{
-		packIDToIndex: make(map[restic.ID]int),
-		mixedPacks:    restic.NewIDSet(),
-		created:       time.Now(),
+		mixedPacks: restic.NewIDSet(),
+		created:    time.Now(),
 	}
 }
 
@@ -402,8 +399,6 @@ func (idx *Index) Finalize() {
 	defer idx.m.Unlock()
 
 	idx.final = true
-	// clear packIDToIndex as no more elements will be added
-	idx.packIDToIndex = nil
 }
 
 // IDs returns the IDs of the index, if available. If the index is not yet