diff --git a/apps/worker/video_processing/unified_render_service.py b/apps/worker/video_processing/unified_render_service.py
index ec25de543..631ba24f5 100755
--- a/apps/worker/video_processing/unified_render_service.py
+++ b/apps/worker/video_processing/unified_render_service.py
@@ -39,7 +39,7 @@ from video_processing.ffmpeg_utils import (
     probe_video_info,
     run_ffmpeg,
 )
-from video_processing.pip_engine import PiPConfig, PiPEngine
+from video_processing.pip_engine import PiPConfig, PiPEngine, PiPLayerConfig
 from video_processing.render_audio import RenderContext, merge_audio_video, mix_audio
 from video_processing.render_subtitles import generate_ass_subtitles
 
@@ -1000,7 +1000,7 @@ class UnifiedRenderService:
 
     # ── 画中画（PiP）相关方法 ──────────────────────────────────────────────────
 
-    def _resolve_pip_sources(self, pip_config: PiPConfig) -> list[tuple[str, "PiPLayerConfig", Path]]:
+    def _resolve_pip_sources(self, pip_config: PiPConfig) -> list[tuple[str, PiPLayerConfig, Path]]:
         """解析画中画图层的素材源，返回可用的图层列表.
 
         降级策略：素材不存在或无效的图层自动跳过，不阻断渲染。