torrent_test.go | 2 ++

diff --git a/torrent_test.go b/torrent_test.go
index 9fe3e96374ff5c3cbe25277b1567d5e92c73587b..51c26c67443f3145c740e578ff263751810cea40 100644
--- a/torrent_test.go
+++ b/torrent_test.go
@@ -142,9 +142,11 @@ 		storageOpener: storage.NewClient(badStorage{}),
 		chunkSize:     2,
 	}
 	require.NoError(t, tt.setInfoBytes(mi.InfoBytes))
+	tt.cl.mu.Lock()
 	tt.pieces[1].DirtyChunks.AddRange(0, 3)
 	require.True(t, tt.pieceAllDirty(1))
 	tt.pieceHashed(1, false)
 	// Dirty chunks should be cleared so we can try again.
 	require.False(t, tt.pieceAllDirty(1))
+	tt.cl.mu.Unlock()
 }