diff --git a/fastapi/_compat.py b/fastapi/_compat.py
index fc605d0ec..13f596423 100644
--- a/fastapi/_compat.py
+++ b/fastapi/_compat.py
@@ -347,6 +347,7 @@ else:
     @dataclass
     class GenerateJsonSchema:  # type: ignore[no-redef]
         ref_template: str
+        by_alias: bool = True
 
     class PydanticSchemaGenerationError(Exception):  # type: ignore[no-redef]
         pass