diff --git a/packages/utils/src/route.js b/packages/utils/src/route.js
index 3c08109d6a2c..95dc8f238ee3 100644
--- a/packages/utils/src/route.js
+++ b/packages/utils/src/route.js
@@ -13,14 +13,19 @@ export const flatRoutes = function flatRoutes (router, fileName = '', routes = [
       if (fileName === '' && r.path === '/') {
         routes.push('/')
       }
+
       return flatRoutes(r.children, fileName + r.path + '/', routes)
     }
     fileName = fileName.replace(/\/+/g, '/')
-    routes.push(
-      (r.path === '' && fileName[fileName.length - 1] === '/'
-        ? fileName.slice(0, -1)
-        : fileName) + r.path
-    )
+
+    // if child path is already absolute, do not make any concatenations
+    if (r.path && r.path.startsWith('/')) {
+      routes.push(r.path)
+    } else if (r.path === '' && fileName[fileName.length - 1] === '/') {
+      routes.push(fileName.slice(0, -1) + r.path)
+    } else {
+      routes.push(fileName + r.path)
+    }
   })
   return routes
 }
diff --git a/packages/utils/test/route.test.js b/packages/utils/test/route.test.js
index 4ec0ee35bffb..7422d55c13f0 100644
--- a/packages/utils/test/route.test.js
+++ b/packages/utils/test/route.test.js
@@ -40,6 +40,37 @@ describe('util: route', () => {
     expect(routes).toEqual(['/', '/foo/bar', '/foo/baz'])
   })
 
+  test('should flat absolute routes', () => {
+    const routes = flatRoutes([
+      {
+        name: 'foo',
+        path: '/foo',
+        children: [
+          { name: 'foo-bar', path: '/foo/bar' },
+          { name: 'foo-baz', path: '/foo/baz' }
+        ]
+      }
+    ])
+
+    expect(routes).toEqual(['/foo/bar', '/foo/baz'])
+  })
+
+  test('should flat absolute routes with empty path', () => {
+    const routes = flatRoutes([
+      {
+        name: 'foo',
+        path: '/foo',
+        children: [
+          { name: 'foo-root', path: '' },
+          { name: 'foo-bar', path: '/foo/bar' },
+          { name: 'foo-baz', path: '/foo/baz' }
+        ]
+      }
+    ])
+
+    expect(routes).toEqual(['/foo', '/foo/bar', '/foo/baz'])
+  })
+
   describe('util: route guard', () => {
     test('should guard parent dir', () => {
       expect(() => {