diff --git a/web_interface/static/v3/js/widgets/custom-feeds.js b/web_interface/static/v3/js/widgets/custom-feeds.js
index 62ed412b..7f52d335 100644
--- a/web_interface/static/v3/js/widgets/custom-feeds.js
+++ b/web_interface/static/v3/js/widgets/custom-feeds.js
@@ -404,9 +404,15 @@
         if (!file) return;
         
         const formData = new FormData();
-        formData.append('file', file);
+        // Backend contract (see api_v3.upload_plugin_asset): the request
+        // field must be named "files" (it does request.files.getlist('files')
+        // and 400s with "No files provided" otherwise), and the response
+        // carries the result in a top-level "uploaded_files" key, not nested
+        // under "data". file-upload-single.js's working upload flow uses this
+        // same contract.
+        formData.append('files', file);
         formData.append('plugin_id', pluginId);
-        
+
         fetch('/api/v3/plugins/assets/upload', {
             method: 'POST',
             body: formData
@@ -421,8 +427,8 @@
             return response.json();
         })
         .then(data => {
-            if (data.status === 'success' && data.data && data.data.files && data.data.files.length > 0) {
-                const uploadedFile = data.data.files[0];
+            if (data.status === 'success' && data.uploaded_files && data.uploaded_files.length > 0) {
+                const uploadedFile = data.uploaded_files[0];
                 const row = document.querySelector(`#${fieldId}_tbody tr[data-index="${index}"]`);
                 if (row) {
                     const logoCell = row.querySelector('td:nth-child(3)');