diff --git a/server/text_generation_server/models/mamba.py b/server/text_generation_server/models/mamba.py
index af09f70f..c10910aa 100644
--- a/server/text_generation_server/models/mamba.py
+++ b/server/text_generation_server/models/mamba.py
@@ -489,10 +489,13 @@ class Mamba(Model):
         generations: List[Generation] = []
         stopped = True
 
+        # Speculation is not active for causal
+        accepted_ids = torch.ones_like(batch.input_ids)[:, 0]
         batch_top_token_ids, batch_top_token_logprobs = batch_top_tokens(
             batch.top_n_tokens,
             batch.top_n_tokens_tensor,
             torch.log_softmax(logits[:, -1], -1),
+            accepted_ids,
         )
 
         start_decode = time.time_ns()