diff --git a/python/sglang/multimodal_gen/runtime/pipelines/flux.py b/python/sglang/multimodal_gen/runtime/pipelines/flux.py
index 371e1c44e..80cd8fe8a 100644
--- a/python/sglang/multimodal_gen/runtime/pipelines/flux.py
+++ b/python/sglang/multimodal_gen/runtime/pipelines/flux.py
@@ -38,7 +38,9 @@ def prepare_mu(batch: Req, server_args: ServerArgs):
     vae_scale_factor = (
         server_args.pipeline_config.vae_config.arch_config.vae_scale_factor
     )
-    image_seq_len = (int(height) // vae_scale_factor) * (int(width) // vae_scale_factor)
+    image_seq_len = (int(height) // (vae_scale_factor * 2)) * (
+        int(width) // (vae_scale_factor * 2)
+    )
 
     mu = calculate_shift(
         image_seq_len,