diff --git a/CHANGELOG.md b/CHANGELOG.md
index 172e95fdf7fe..e6bb0aed5226 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Fixed
 
 - _Experimental_: Improve codemod output, keep CSS after last Tailwind directive unlayered ([#14512](https://github.com/tailwindlabs/tailwindcss/pull/14512))
+- _Experimental_: Fix incorrect empty `layer()` at the end of `@import` at-rules when running codemods ([#14513](https://github.com/tailwindlabs/tailwindcss/pull/14513))
 
 ## [4.0.0-alpha.25] - 2024-09-24
 
diff --git a/packages/@tailwindcss-upgrade/src/codemods/migrate-missing-layers.test.ts b/packages/@tailwindcss-upgrade/src/codemods/migrate-missing-layers.test.ts
index 9cae49b04fd7..4fd81cf6d48e 100644
--- a/packages/@tailwindcss-upgrade/src/codemods/migrate-missing-layers.test.ts
+++ b/packages/@tailwindcss-upgrade/src/codemods/migrate-missing-layers.test.ts
@@ -14,6 +14,14 @@ function migrate(input: string) {
     .then((result) => result.css)
 }
 
+it('should not migrate already migrated `@import` at-rules', async () => {
+  expect(
+    await migrate(css`
+      @import 'tailwindcss';
+    `),
+  ).toMatchInlineSnapshot(`"@import 'tailwindcss';"`)
+})
+
 it('should migrate rules between tailwind directives', async () => {
   expect(
     await migrate(css`
diff --git a/packages/@tailwindcss-upgrade/src/codemods/migrate-missing-layers.ts b/packages/@tailwindcss-upgrade/src/codemods/migrate-missing-layers.ts
index 39f60e4cf1a9..4e25656d95b0 100644
--- a/packages/@tailwindcss-upgrade/src/codemods/migrate-missing-layers.ts
+++ b/packages/@tailwindcss-upgrade/src/codemods/migrate-missing-layers.ts
@@ -65,7 +65,7 @@ export function migrateMissingLayers(): Plugin {
 
         // Add layer to `@import` at-rules
         if (node.name === 'import') {
-          if (!node.params.includes('layer(')) {
+          if (lastLayer !== '' && !node.params.includes('layer(')) {
             node.params += ` layer(${lastLayer})`
           }