diff --git a/api/onnx_web/chain/blend_mask.py b/api/onnx_web/chain/blend_mask.py
index f85fad1d..93abd1ee 100644
--- a/api/onnx_web/chain/blend_mask.py
+++ b/api/onnx_web/chain/blend_mask.py
@@ -37,7 +37,7 @@ class BlendMaskStage(BaseStage):
         mult_mask = Image.alpha_composite(mult_mask, mask_source)
         mult_mask = mult_mask.convert("L")
 
-        top, left, tile = dims
+        left, top, tile = dims
         stage_source_tile = stage_source.crop((left, top, left + tile, top + tile))
 
         if is_debug():