diff --git a/python/sglang/srt/managers/schedule_batch.py b/python/sglang/srt/managers/schedule_batch.py
index 5068c79361c..25770c6ae93 100644
--- a/python/sglang/srt/managers/schedule_batch.py
+++ b/python/sglang/srt/managers/schedule_batch.py
@@ -182,6 +182,7 @@ def merge(self, other):
         optional_args = [
             "image_sizes",
             "image_offsets",
+            "image_pad_len",
             # "modalities", # modalities should be ["multi-images"] (one entry) even for multiple images
             "aspect_ratio_ids",
             "aspect_ratio_mask",