diff --git a/vllm/sampling_params.py b/vllm/sampling_params.py
index f6e7a3ca..5fa94eb1 100644
--- a/vllm/sampling_params.py
+++ b/vllm/sampling_params.py
@@ -139,7 +139,10 @@ class SamplingParams:
         self.top_p = top_p
         self.top_k = top_k
         self.min_p = min_p
-        self.seed = seed
+        if seed == -1:
+            self.seed = None
+        else:
+            self.seed = seed
         self.use_beam_search = use_beam_search
         self.length_penalty = length_penalty
         self.early_stopping = early_stopping