diff --git a/vllm/distributed/kv_transfer/kv_connector/v1/base.py b/vllm/distributed/kv_transfer/kv_connector/v1/base.py
index 8e9182a9bca4..91f6443f92cb 100644
--- a/vllm/distributed/kv_transfer/kv_connector/v1/base.py
+++ b/vllm/distributed/kv_transfer/kv_connector/v1/base.py
@@ -239,7 +239,7 @@ class KVConnectorBase_V1(ABC):
         return
 
     def register_cross_layers_kv_cache(
-        self, kv_cache: torch.Tensor, attn_backend: type[AttentionBackend]
+        self, kv_cache: torch.Tensor, attn_backend: type["AttentionBackend"]
     ):
         """
         Initialize with a single KV cache tensor used by all layers.