diff --git a/client/src/api/schema/schema.ts b/client/src/api/schema/schema.ts
index d55c9b73f17c..b7b237c6a7ad 100644
--- a/client/src/api/schema/schema.ts
+++ b/client/src/api/schema/schema.ts
@@ -11665,6 +11665,7 @@ export interface components {
              * @description A list of content items to update with the changes.
              */
             items: components["schemas"]["UpdateContentItem"][];
+            [key: string]: unknown | undefined;
         };
         /**
          * UpdateHistoryContentsPayload
diff --git a/lib/galaxy/schema/schema.py b/lib/galaxy/schema/schema.py
index 8bc60b8f9dc8..c22f5353c20e 100644
--- a/lib/galaxy/schema/schema.py
+++ b/lib/galaxy/schema/schema.py
@@ -1100,20 +1100,19 @@ class UpdateContentItem(HistoryContentItem):
 class UpdateHistoryContentsBatchPayload(Model):
     """Contains property values that will be updated for all the history `items` provided."""
 
-    model_config = ConfigDict(extra="allow")
-
     items: List[UpdateContentItem] = Field(
         ...,
         title="Items",
         description="A list of content items to update with the changes.",
     )
     model_config = ConfigDict(
+        extra="allow",
         json_schema_extra={
             "example": {
                 "items": [{"history_content_type": "dataset", "id": "string"}],
                 "visible": False,
             }
-        }
+        },
     )