diff --git a/qfieldsync/core/layer.py b/qfieldsync/core/layer.py
index 0c7ee8a6..9b71f187 100644
--- a/qfieldsync/core/layer.py
+++ b/qfieldsync/core/layer.py
@@ -283,6 +283,7 @@ def visible_fields_names(self, items = None):
             if hasattr(item, 'children'):
                 result += self.visible_fields_names(item.children())
             elif isinstance(item, QgsAttributeEditorField):
-                result.append(fields.at(item.idx()).name())
+                if item.idx() >= 0:
+                    result.append(fields.at(item.idx()).name())
 
         return result