diff --git a/python/sglang/srt/managers/schedule_batch.py b/python/sglang/srt/managers/schedule_batch.py
index 98fc5581c..f4d41feef 100644
--- a/python/sglang/srt/managers/schedule_batch.py
+++ b/python/sglang/srt/managers/schedule_batch.py
@@ -144,7 +144,7 @@ class ImageInputs:
         ]
         ret.image_sizes = obj["image_sizes"]
         # Only when pixel values is not None we have modalities
-        ret.modalities = obj["modalities"]
+        ret.modalities = obj["modalities"] or ["image"]
         return ret