diff --git a/extern/sector-storage/sched.go b/extern/sector-storage/sched.go
index 16e51f9a6..56d78bfae 100644
--- a/extern/sector-storage/sched.go
+++ b/extern/sector-storage/sched.go
@@ -641,7 +641,7 @@ func (sh *scheduler) workerCompactWindows(worker *workerHandle, wid WorkerID) in
 			if len(moved) > 0 {
 				newTodo := make([]*workerRequest, 0, len(window.todo)-len(moved))
 				for i, t := range window.todo {
-					if moved[0] == i {
+					if len(moved) > 0 && moved[0] == i {
 						moved = moved[1:]
 						continue
 					}
diff --git a/extern/sector-storage/sched_test.go b/extern/sector-storage/sched_test.go
index 4aa1dc49b..08fdbe38f 100644
--- a/extern/sector-storage/sched_test.go
+++ b/extern/sector-storage/sched_test.go
@@ -637,4 +637,9 @@ func TestWindowCompact(t *testing.T) {
 		[][]sealtasks.TaskType{{sealtasks.TTPreCommit1, sealtasks.TTPreCommit1}, {sealtasks.TTPreCommit1, sealtasks.TTAddPiece}},
 		[][]sealtasks.TaskType{{sealtasks.TTPreCommit1, sealtasks.TTPreCommit1, sealtasks.TTAddPiece}, {sealtasks.TTPreCommit1}}),
 	)
+
+	t.Run("2pc1-pc1appc2", test(
+		[][]sealtasks.TaskType{{sealtasks.TTPreCommit1, sealtasks.TTPreCommit1}, {sealtasks.TTPreCommit1, sealtasks.TTAddPiece, sealtasks.TTPreCommit2}},
+		[][]sealtasks.TaskType{{sealtasks.TTPreCommit1, sealtasks.TTPreCommit1, sealtasks.TTAddPiece}, {sealtasks.TTPreCommit1, sealtasks.TTPreCommit2}}),
+	)
 }