diff --git a/elasticsearch/esql/esql.py b/elasticsearch/esql/esql.py
index 05f4e3e3e..367ec971d 100644
--- a/elasticsearch/esql/esql.py
+++ b/elasticsearch/esql/esql.py
@@ -124,7 +124,7 @@ def _format_id(id: FieldType, allow_patterns: bool = False) -> str:
         if re.fullmatch(r"[a-zA-Z_@][a-zA-Z0-9_\.]*", s):
             return s
         # this identifier needs to be escaped
-        s.replace("`", "``")
+        s = s.replace("`", "``")
         return f"`{s}`"
 
     @staticmethod