diff --git a/python/sglang/srt/managers/tp_worker.py b/python/sglang/srt/managers/tp_worker.py
index 33acf98e8..d7dedc29d 100644
--- a/python/sglang/srt/managers/tp_worker.py
+++ b/python/sglang/srt/managers/tp_worker.py
@@ -364,12 +364,13 @@ class ModelTpServer:
         # Compute matched prefix length
         for req in self.waiting_queue:
             req.input_ids = req.origin_input_ids + req.output_ids
-            prefix_indices, last_node = self.tree_cache.match_prefix(
-                rid=req.rid,
-                key=req.input_ids,
-            )
+            try_match_ids = req.input_ids
             if req.return_logprob:
-                prefix_indices = prefix_indices[: req.logprob_start_len]
+                try_match_ids = req.input_ids[: req.logprob_start_len]
+            # NOTE: the prefix_indices must always be aligned with last_node
+            prefix_indices, last_node = self.tree_cache.match_prefix(
+                rid=req.rid, key=try_match_ids
+            )
             req.extend_input_len = len(req.input_ids) - len(prefix_indices)
             req.prefix_indices = prefix_indices
             req.last_node = last_node