diff --git a/nanovllm/engine/block_manager.py b/nanovllm/engine/block_manager.py
index 65d725e..763aae2 100644
--- a/nanovllm/engine/block_manager.py
+++ b/nanovllm/engine/block_manager.py
@@ -88,6 +88,7 @@ class BlockManager:
             if block.ref_count == 0:
                 self._deallocate_block(block_id)
         seq.num_cached_tokens = 0
+        seq.prefilled = False
         seq.block_table.clear()
 
     def can_append(self, seq: Sequence) -> bool:
diff --git a/nanovllm/engine/sequence.py b/nanovllm/engine/sequence.py
index 49d9ee6..e12f30d 100644
--- a/nanovllm/engine/sequence.py
+++ b/nanovllm/engine/sequence.py
@@ -27,6 +27,7 @@ class Sequence:
         self.temperature = sampling_params.temperature
         self.max_tokens = sampling_params.max_tokens
         self.ignore_eos = sampling_params.ignore_eos
+        self.prefilled = False
 
     def __len__(self):
         return self.num_tokens
@@ -70,14 +71,15 @@ class Sequence:
         self.token_ids.append(token_id)
         self.last_token = token_id
         self.num_tokens += 1
+        self.prefilled = True
 
     def __getstate__(self):
-        return (self.num_tokens, self.num_prompt_tokens, self.num_cached_tokens, self.block_table,
-                self.token_ids if self.num_completion_tokens == 0 else self.last_token)
+        return (self.num_tokens, self.num_prompt_tokens, self.num_cached_tokens, self.block_table, self.prefilled,
+                self.last_token if self.prefilled else self.token_ids)
 
     def __setstate__(self, state):
-        self.num_tokens, self.num_prompt_tokens, self.num_cached_tokens, self.block_table = state[:-1]
-        if self.num_completion_tokens == 0:
-            self.token_ids = state[-1]
-        else:
+        self.num_tokens, self.num_prompt_tokens, self.num_cached_tokens, self.block_table, self.prefilled = state[:-1]
+        if self.prefilled:
             self.last_token = state[-1]
+        else:
+            self.token_ids = state[-1]