diff --git a/saxml/server/model_service_base.py b/saxml/server/model_service_base.py
index f73bdede..41b8bbae 100644
--- a/saxml/server/model_service_base.py
+++ b/saxml/server/model_service_base.py
@@ -1336,11 +1336,11 @@ def _generate_rng_seed(self):
   def _encode_message(self, *msgs: str) -> str:
     assert msgs
     for m in msgs:
-      assert '\u2581' not in m
-    return '\u2581'.join(msgs)
+      assert '|' not in m
+    return '|'.join(msgs)
 
   def _decode_message(self, encoded: str) -> List[str]:
-    return encoded.split('\u2581')
+    return encoded.split('|')
 
   def _load_model(
       self,