diff --git a/fastapi/_compat/v2.py b/fastapi/_compat/v2.py
index 6c3cf2af4c..777a22281f 100644
--- a/fastapi/_compat/v2.py
+++ b/fastapi/_compat/v2.py
@@ -44,6 +44,8 @@ evaluate_forwardref = eval_type_lenient
 class GenerateJsonSchema(_GenerateJsonSchema):
     def bytes_schema(self, schema: CoreSchema) -> JsonSchemaValue:
         json_schema = {"type": "string", "contentMediaType": "application/octet-stream"}
+        if self._config.ser_json_bytes == "base64":
+            json_schema["contentEncoding"] = "base64"
         self.update_with_validations(json_schema, schema, self.ValidationsMapping.bytes)
         return json_schema