diff --git a/backend/nn/flux.py b/backend/nn/flux.py
index 942d9c33..097e6622 100644
--- a/backend/nn/flux.py
+++ b/backend/nn/flux.py
@@ -372,7 +372,7 @@ class IntegratedFluxTransformer2DModel(nn.Module):
         del vec
         return img
 
-    def forward(self, x, timestep, context, y, guidance, **kwargs):
+    def forward(self, x, timestep, context, y, guidance=None, **kwargs):
         bs, c, h, w = x.shape
         input_device = x.device
         input_dtype = x.dtype