diff --git a/nanovllm/engine/model_runner.py b/nanovllm/engine/model_runner.py
index 5e6342b..c58f619 100644
--- a/nanovllm/engine/model_runner.py
+++ b/nanovllm/engine/model_runner.py
@@ -139,8 +139,8 @@ class ModelRunner:
             seqlen = len(seq)
             start = min(seq.num_cached_tokens, seqlen - 1)
             seqlen_q = seq.num_scheduled_tokens
-            seqlen_k = seqlen
             end = start + seqlen_q
+            seqlen_k = end
             input_ids.extend(seq[start:end])
             positions.extend(range(start, end))
             cu_seqlens_q.append(cu_seqlens_q[-1] + seqlen_q)