diff --git a/vllm/transformers_utils/configs/speculators/algos.py b/vllm/transformers_utils/configs/speculators/algos.py
index f4b0f73f62..e034cec974 100644
--- a/vllm/transformers_utils/configs/speculators/algos.py
+++ b/vllm/transformers_utils/configs/speculators/algos.py
@@ -120,6 +120,10 @@ def update_dflash(config_dict: dict, pre_trained_config: dict) -> None:
         "mask_token_id": config_dict["mask_token_id"],
         "target_layer_ids": [i - 1 for i in aux_layer_ids],
     }
+    # Enable causal masking in SWA for vllm-project/speculators models
+    pre_trained_config["dflash_config"]["causal"] = not config_dict.get(
+        "sliding_window_non_causal", True
+    )
 
 
 @register_speculator("dspark")