diff --git a/storage/aws/aws.go b/storage/aws/aws.go
index 08f2ebac..6ad61ba8 100644
--- a/storage/aws/aws.go
+++ b/storage/aws/aws.go
@@ -629,6 +629,9 @@ func (m *MigrationStorage) fetchLeafHashes(ctx context.Context, from, to, source
 			if err != nil {
 				return fmt.Errorf("bundleHasherFunc for bundle index %d: %v", ri.Index, err)
 			}
+			if l := len(bh); l < int(ri.First+ri.N) {
+				return fmt.Errorf("bundle index %d has fewer entries than expected (%d < %d)", ri.Index, l, ri.First+ri.N)
+			}
 			toBeAdded.Store(ri.Index, bh[ri.First:ri.First+ri.N])
 			return nil
 		})
diff --git a/storage/gcp/gcp.go b/storage/gcp/gcp.go
index 7e74da7b..3a97acd2 100644
--- a/storage/gcp/gcp.go
+++ b/storage/gcp/gcp.go
@@ -1535,6 +1535,9 @@ func (m *MigrationStorage) fetchLeafHashes(ctx context.Context, from, to, source
 			if err != nil {
 				return fmt.Errorf("bundleHasherFunc for bundle index %d: %v", ri.Index, err)
 			}
+			if l := len(bh); l < int(ri.First+ri.N) {
+				return fmt.Errorf("bundle index %d has fewer entries than expected (%d < %d)", ri.Index, l, ri.First+ri.N)
+			}
 			toBeAdded.Store(ri.Index, bh[ri.First:ri.First+ri.N])
 			return nil
 		})
diff --git a/storage/posix/files.go b/storage/posix/files.go
index e7117083..560c08c0 100644
--- a/storage/posix/files.go
+++ b/storage/posix/files.go
@@ -1116,6 +1116,9 @@ func (m *MigrationStorage) fetchLeafHashes(ctx context.Context, from, to, source
 		if err != nil {
 			return nil, fmt.Errorf("bundleHasherFunc for bundle index %d: %v", ri.Index, err)
 		}
+		if l := len(bh); l < int(ri.First+ri.N) {
+			return nil, fmt.Errorf("bundle index %d has fewer entries than expected (%d < %d)", ri.Index, l, ri.First+ri.N)
+		}
 		lh = append(lh, bh[ri.First:ri.First+ri.N]...)
 		n++
 		if n >= maxBundles {