diff --git a/internal/repository/repository.go b/internal/repository/repository.go
index f26226ffd..33eab8cb0 100644
--- a/internal/repository/repository.go
+++ b/internal/repository/repository.go
@@ -163,12 +163,6 @@ func (r *Repository) SetDryRun() {
 	r.be = dryrun.New(r.be)
 }
 
-// PrefixLength returns the number of bytes required so that all prefixes of
-// all IDs of type t are unique.
-func (r *Repository) PrefixLength(ctx context.Context, t restic.FileType) (int, error) {
-	return restic.PrefixLength(ctx, r.be, t)
-}
-
 // LoadUnpacked loads and decrypts the file with the given type and ID, using
 // the supplied buffer (which must be empty). If the buffer is nil, a new
 // buffer will be allocated and returned.
diff --git a/internal/restic/backend_find.go b/internal/restic/backend_find.go
index 4be2f523f..8ce57dd1d 100644
--- a/internal/restic/backend_find.go
+++ b/internal/restic/backend_find.go
@@ -61,42 +61,3 @@ func Find(ctx context.Context, be Lister, t FileType, prefix string) (string, er
 
 	return "", &NoIDByPrefixError{prefix}
 }
-
-const minPrefixLength = 8
-
-// PrefixLength returns the number of bytes required so that all prefixes of
-// all names of type t are unique.
-func PrefixLength(ctx context.Context, be Lister, t FileType) (int, error) {
-	// load all IDs of the given type
-	list := make([]string, 0, 100)
-
-	ctx, cancel := context.WithCancel(ctx)
-	defer cancel()
-
-	err := be.List(ctx, t, func(fi FileInfo) error {
-		list = append(list, fi.Name)
-		return nil
-	})
-
-	if err != nil {
-		return 0, err
-	}
-
-	// select prefixes of length l, test if the last one is the same as the current one
-	var id ID
-outer:
-	for l := minPrefixLength; l < len(id); l++ {
-		var last string
-
-		for _, name := range list {
-			if last == name[:l] {
-				continue outer
-			}
-			last = name[:l]
-		}
-
-		return l, nil
-	}
-
-	return len(id), nil
-}
diff --git a/internal/restic/backend_find_test.go b/internal/restic/backend_find_test.go
index 52eb38ef3..bd1e6f7e6 100644
--- a/internal/restic/backend_find_test.go
+++ b/internal/restic/backend_find_test.go
@@ -75,44 +75,3 @@ func TestFind(t *testing.T) {
 		t.Errorf("Find should not return a match on error.")
 	}
 }
-
-func TestPrefixLength(t *testing.T) {
-	list := samples
-
-	m := mockBackend{}
-	m.list = func(ctx context.Context, t FileType, fn func(FileInfo) error) error {
-		for _, id := range list {
-			err := fn(FileInfo{Name: id.String()})
-			if err != nil {
-				return err
-			}
-		}
-		return nil
-	}
-
-	l, err := PrefixLength(context.TODO(), m, SnapshotFile)
-	if err != nil {
-		t.Error(err)
-	}
-	if l != 19 {
-		t.Errorf("wrong prefix length returned, want %d, got %d", 19, l)
-	}
-
-	list = samples[:3]
-	l, err = PrefixLength(context.TODO(), m, SnapshotFile)
-	if err != nil {
-		t.Error(err)
-	}
-	if l != 19 {
-		t.Errorf("wrong prefix length returned, want %d, got %d", 19, l)
-	}
-
-	list = samples[3:]
-	l, err = PrefixLength(context.TODO(), m, SnapshotFile)
-	if err != nil {
-		t.Error(err)
-	}
-	if l != 8 {
-		t.Errorf("wrong prefix length returned, want %d, got %d", 8, l)
-	}
-}