diff --git a/list/src/org/labkey/list/model/ListWriter.java b/list/src/org/labkey/list/model/ListWriter.java
index 74ada5acdc5..e161128d659 100644
--- a/list/src/org/labkey/list/model/ListWriter.java
+++ b/list/src/org/labkey/list/model/ListWriter.java
@@ -474,6 +474,11 @@ public void writeColumn(ColumnInfo column, ColumnType columnXml)
                     // Write URL, if exists, from property descriptor
                     if (null != propertyDescriptor.getURL())
                         columnXml.setUrl(propertyDescriptor.getURL().toXML());
+                    else if (column.getPropertyType() == PropertyType.ATTACHMENT)
+                    {
+                        // Issue 53505 : don't serialize the download URL if it wasn't set on the property descriptor
+                        columnXml.unsetUrl();
+                    }
                 }
             }
         }