diff --git a/boiling_learning/preprocessing/video.py b/boiling_learning/preprocessing/video.py
index b4543548..c9b26b1f 100644
--- a/boiling_learning/preprocessing/video.py
+++ b/boiling_learning/preprocessing/video.py
@@ -24,6 +24,8 @@
     VideoFrameF32 = npt.NDArray[np.float32]
     VideoFrame = Union[VideoFrameU8, VideoFrameF32]
 else:
+    VideoFrameU8 = np.ndarray
+    VideoFrameF32 = np.ndarray
     VideoFrame = np.ndarray