diff --git a/tasks/gulp/__tests__/after-build-dist.test.mjs b/tasks/gulp/__tests__/after-build-dist.test.mjs
index 8993ce7749..f9ef4c4f4c 100644
--- a/tasks/gulp/__tests__/after-build-dist.test.mjs
+++ b/tasks/gulp/__tests__/after-build-dist.test.mjs
@@ -50,14 +50,20 @@ describe('dist/', () => {
   })
 
   describe('govuk-frontend-[version].min.js', () => {
+    let filename
     let javascript
 
     beforeAll(async () => {
-      javascript = await readFile(join(configPaths.dist, `govuk-frontend-${pkg.version}.min.js`), 'utf8')
+      filename = `govuk-frontend-${pkg.version}.min.js`
+      javascript = await readFile(join(configPaths.dist, filename), 'utf8')
     })
 
     it('should have the correct version name', () => {
       expect(javascript).toBeTruthy()
     })
+
+    it('should contain source mapping URL', () => {
+      expect(javascript).toMatch(new RegExp(`//# sourceMappingURL=${filename}.map$`))
+    })
   })
 })
diff --git a/tasks/gulp/__tests__/after-build-package.test.mjs b/tasks/gulp/__tests__/after-build-package.test.mjs
index d4ae6b697c..28b30a9a40 100644
--- a/tasks/gulp/__tests__/after-build-package.test.mjs
+++ b/tasks/gulp/__tests__/after-build-package.test.mjs
@@ -51,7 +51,10 @@ describe('package/', () => {
         const importFilter = /^govuk(?!-)/
 
         // All source `**/*.mjs` files compiled to `**/*.js`
-        const output = [join(requirePath, `${name}.js`)]
+        const output = [
+          join(requirePath, `${name}.js`),
+          join(requirePath, `${name}.js.map`) // with source map
+        ]
 
         // Only source `./govuk/**/*.mjs` files copied to `./govuk-esm/**/*.mjs`
         if (importFilter.test(requirePath)) {
diff --git a/tasks/gulp/compile-assets.mjs b/tasks/gulp/compile-assets.mjs
index 301141444f..857abf1838 100644
--- a/tasks/gulp/compile-assets.mjs
+++ b/tasks/gulp/compile-assets.mjs
@@ -136,8 +136,12 @@ export async function compileJavaScripts () {
       ? componentNameToJavaScriptModuleName(name)
       : 'GOVUKFrontend'
 
-    return compileJavaScript(gulp.src(slash(join(configPaths.src, file))), moduleName)
-      .pipe(gulp.dest(slash(join(destPath, modulePath))))
+    return compileJavaScript(gulp.src(slash(join(configPaths.src, file)), {
+      sourcemaps: true
+    }), moduleName)
+      .pipe(gulp.dest(slash(join(destPath, modulePath)), {
+        sourcemaps: '.'
+      }))
   }))
 }