diff --git a/packages/libs/lambda-at-edge/src/default-handler.ts b/packages/libs/lambda-at-edge/src/default-handler.ts
index 4af8b03ee0..3183df0ba0 100644
--- a/packages/libs/lambda-at-edge/src/default-handler.ts
+++ b/packages/libs/lambda-at-edge/src/default-handler.ts
@@ -386,7 +386,7 @@ const handleOriginResponse = async ({
           request,
           pageS3Path: s3Uri,
           eTag: response.headers["etag"]?.[0].value,
-          lastModified: response.headers["etag"]?.[0].value,
+          lastModified: response.headers["last-modified"]?.[0].value,
           pagePath: staticRoute.page,
           queueName: regenerationQueueName
         });
diff --git a/packages/libs/lambda-at-edge/src/lib/triggerStaticRegeneration.ts b/packages/libs/lambda-at-edge/src/lib/triggerStaticRegeneration.ts
index beb45e2936..f0e36364f3 100644
--- a/packages/libs/lambda-at-edge/src/lib/triggerStaticRegeneration.ts
+++ b/packages/libs/lambda-at-edge/src/lib/triggerStaticRegeneration.ts
@@ -57,11 +57,9 @@ export const triggerStaticRegeneration = async (
         // We only want to trigger the regeneration once for every previous
         // update. This will prevent the case where this page is being
         // requested again whilst its already started to regenerate.
-        MessageDeduplicationId:
-          options.eTag ??
-          (options.lastModified
-            ? new Date(options.lastModified).getTime().toString()
-            : new Date().getTime().toString()),
+        MessageDeduplicationId: options.lastModified
+          ? new Date(options.lastModified).getTime().toString()
+          : options.eTag ?? new Date().getTime().toString(),
         // Only deduplicate based on the object, i.e. we can generate
         // different pages in parallel, just not the same one
         MessageGroupId: hashedUri
diff --git a/packages/libs/lambda-at-edge/tests/utils/triggerStaticRegeneration.test.ts b/packages/libs/lambda-at-edge/tests/utils/triggerStaticRegeneration.test.ts
index 589b504a5e..8678d63775 100644
--- a/packages/libs/lambda-at-edge/tests/utils/triggerStaticRegeneration.test.ts
+++ b/packages/libs/lambda-at-edge/tests/utils/triggerStaticRegeneration.test.ts
@@ -90,9 +90,9 @@ describe("triggerStaticRegeneration()", () => {
   });
 
   it.each`
-    lastModified                  | etag         | expected
-    ${"2021-05-05T17:15:04.472Z"} | ${"tag"}     | ${"tag"}
-    ${"2021-05-05T17:15:04.472Z"} | ${undefined} | ${"1620234904472"}
+    lastModified                  | etag     | expected
+    ${"2021-05-05T17:15:04.472Z"} | ${"tag"} | ${"1620234904472"}
+    ${undefined}                  | ${"tag"} | ${"tag"}
   `(
     "should throttle send correct parameters to the queue",
     async ({ lastModified, etag, expected }) => {