diff --git a/vllm/multimodal/hasher.py b/vllm/multimodal/hasher.py
index cc50322fe..7f0c6d134 100644
--- a/vllm/multimodal/hasher.py
+++ b/vllm/multimodal/hasher.py
@@ -98,6 +98,9 @@ class MultiModalHasher:
         key: str,
         obj: object,
     ) -> Iterable[bytes | memoryview]:
+        if obj is None:
+            yield key.encode("utf-8")
+            return
         # Recursive cases
         if isinstance(obj, (list, tuple)):
             for i, elem in enumerate(obj):