diff --git a/src/lib/elements/element_data_store.svelte b/src/lib/elements/element_data_store.svelte
index 1a085036..861bc6b8 100644
--- a/src/lib/elements/element_data_store.svelte
+++ b/src/lib/elements/element_data_store.svelte
@@ -278,8 +278,13 @@ async function handle_submit_form(event: Event) {
     }
 
     const api_cfg = untrack(() => $ae_api);
-    const api_call = $lq__ds_obj?.id 
-        ? api.update_ae_obj({ api_cfg, obj_type: 'data_store', obj_id: $lq__ds_obj.id, fields: data_store_do })
+    // for_type and for_id are parent-context fields set at creation time; never send them on update
+    // (for_id is an integer FK in the DB — sending a string random ID causes a 400 error).
+    const update_do: key_val = { ...data_store_do };
+    delete update_do.for_type;
+    delete update_do.for_id;
+    const api_call = $lq__ds_obj?.id
+        ? api.update_ae_obj({ api_cfg, obj_type: 'data_store', obj_id: $lq__ds_obj.id, fields: update_do })
         : api.create_ae_obj({ api_cfg, obj_type: 'data_store', fields: data_store_do });
 
     api_call.then((res) => {