diff --git a/lib/file-share-stack.ts b/lib/file-share-stack.ts
index 1d955a8..7b85d7c 100644
--- a/lib/file-share-stack.ts
+++ b/lib/file-share-stack.ts
@@ -193,8 +193,10 @@ export class FileShareStack extends cdk.Stack {
           name: "file-share-nightly",
           createRule: { interval: 24, intervalUnit: "HOURS", times: ["06:00"] },
           retainRule: { count: 30 },
+          // copyTags already propagates file-share-backup=true from the volume to each
+          // snapshot; an explicit tagsToAdd of the same key triggers DLM's duplicate-tag
+          // error ("Tag file-share-backup is already defined") and puts the policy in ERROR.
           copyTags: true,
-          tagsToAdd: [{ key: "file-share-backup", value: "true" }],
         }],
       },
     });