diff --git a/jest.config.js b/jest.config.js
index 3fc6d20fa0dc3e..4e0a5fac509b8a 100644
--- a/jest.config.js
+++ b/jest.config.js
@@ -1,3 +1,4 @@
 module.exports = {
+  testPathIgnorePatterns: ['/playground/', '/node_modules/'],
   watchPathIgnorePatterns: ['<rootDir>/temp']
 }
diff --git a/package.json b/package.json
index 6b053d1169df8d..ffb606ce92a670 100644
--- a/package.json
+++ b/package.json
@@ -97,6 +97,7 @@
     "ws": "^7.2.3"
   },
   "devDependencies": {
+    "@babel/runtime": "7.10.2",
     "@pika/react": "^16.13.1",
     "@pika/react-dom": "^16.13.1",
     "@types/es-module-lexer": "^0.3.0",
diff --git a/playground/App.vue b/playground/App.vue
index c9ea18f1aee0fa..792589a22dd9c5 100644
--- a/playground/App.vue
+++ b/playground/App.vue
@@ -26,6 +26,8 @@
   <TestRewriteOptimized />
   <TestCustomBlocks />
   <TestOptimizeLink />
+  <TestRewriteUnoptimized />
+  <TestNormalizePublicPath />
 </template>
 
 <script>
@@ -48,6 +50,8 @@ import TestRewriteOptimized from './rewrite-optimized/TestRewriteOptimized.vue'
 import TestCssAtImport from './css-@import/TestCssAtImport.vue'
 import TestCustomBlocks from './custom-blocks/TestCustomBlocks.vue'
 import TestOptimizeLink from './optimize-linked/TestOptimizeLink.vue'
+import TestRewriteUnoptimized from './rewrite-unoptimized/TestRewriteUnoptimized.vue'
+import TestNormalizePublicPath from './TestNormalizePublicPath.vue'
 
 export default {
   data: () => ({
@@ -73,7 +77,9 @@ export default {
     TestAsync: defineAsyncComponent(() => import('./TestAsync.vue')),
     TestRewriteOptimized,
     TestCustomBlocks,
-    TestOptimizeLink
+    TestOptimizeLink,
+    TestRewriteUnoptimized,
+    TestNormalizePublicPath
   }
 }
 </script>
diff --git a/playground/TestHmr/TestHmr.vue b/playground/TestHmr/TestHmr.vue
index a6c4f3575c8872..fbff720728e731 100644
--- a/playground/TestHmr/TestHmr.vue
+++ b/playground/TestHmr/TestHmr.vue
@@ -52,8 +52,7 @@
     <span
       class="hmr-propagation-full-dynamic-self-accepting"
       ref="dynamicDataOutlet"
-      >qux not loaded</span
-    >
+      >qux not loaded</span>
     <button
       class="hmr-propagation-full-dynamic-load-self-accepting"
       @click="loadFullDynamicSelfAccepting()"
diff --git a/playground/TestNormalizePublicPath.vue b/playground/TestNormalizePublicPath.vue
new file mode 100644
index 00000000000000..eb1157ed3764aa
--- /dev/null
+++ b/playground/TestNormalizePublicPath.vue
@@ -0,0 +1,21 @@
+<template>
+  <h2>TestNormalizePublicPath</h2>
+  <p class="normalize-public-path">{{ msg }}</p>
+</template>
+
+<script>
+import slicedToArray from '@babel/runtime/helpers/esm/slicedToArray'
+
+const iterable = (function* () {
+  yield 2
+  yield 4
+  yield 6
+  yield 8
+})()
+
+export default {
+  data: () => ({
+    msg: JSON.stringify(slicedToArray(iterable, 2))
+  })
+}
+</script>
diff --git a/playground/package.json b/playground/package.json
index 6f4edbf9c3b64c..6a32f580a0e581 100644
--- a/playground/package.json
+++ b/playground/package.json
@@ -8,9 +8,11 @@
     "bootstrap": "link:../node_modules/bootstrap",
     "lodash-es": "link:../node_modules/lodash-es",
     "moment": "link:../node_modules/moment",
+    "@babel/runtime": "link:../node_modules/@babel/runtime",
     "normalize.css": "link:../node_modules/normalize.css",
     "resolve-browser-field-test-package": "link:./resolve-browser-field",
     "rewrite-optimized-test-package": "link:./rewrite-optimized/test-package",
-    "optimize-linked": "link:./optimize-linked"
+    "optimize-linked": "link:./optimize-linked",
+    "rewrite-unoptimized-test-package": "link:./rewrite-unoptimized/test-package"
   }
 }
diff --git a/playground/rewrite-unoptimized/TestRewriteUnoptimized.vue b/playground/rewrite-unoptimized/TestRewriteUnoptimized.vue
new file mode 100644
index 00000000000000..3838856ce44943
--- /dev/null
+++ b/playground/rewrite-unoptimized/TestRewriteUnoptimized.vue
@@ -0,0 +1,12 @@
+<template>
+  <h2>Test rewrite in optimized module</h2>
+  <p class="test-rewrite-in-unoptimized">{{ msg }}</p>
+</template>
+
+<script>
+import value from 'rewrite-unoptimized-test-package'
+
+export default {
+  data: () => ({ msg: value })
+}
+</script>
diff --git a/playground/rewrite-unoptimized/test-package/es/index.js b/playground/rewrite-unoptimized/test-package/es/index.js
new file mode 100644
index 00000000000000..ba1501c042ee11
--- /dev/null
+++ b/playground/rewrite-unoptimized/test-package/es/index.js
@@ -0,0 +1,3 @@
+import { Item } from './nested'
+
+export default Item
diff --git a/playground/rewrite-unoptimized/test-package/es/nested/foo.js b/playground/rewrite-unoptimized/test-package/es/nested/foo.js
new file mode 100644
index 00000000000000..fb5230a12964fa
--- /dev/null
+++ b/playground/rewrite-unoptimized/test-package/es/nested/foo.js
@@ -0,0 +1 @@
+export default 123
diff --git a/playground/rewrite-unoptimized/test-package/es/nested/index.js b/playground/rewrite-unoptimized/test-package/es/nested/index.js
new file mode 100644
index 00000000000000..e13ecfa276720f
--- /dev/null
+++ b/playground/rewrite-unoptimized/test-package/es/nested/index.js
@@ -0,0 +1 @@
+export { default as Item } from './foo'
diff --git a/playground/rewrite-unoptimized/test-package/package.json b/playground/rewrite-unoptimized/test-package/package.json
new file mode 100644
index 00000000000000..264b7f760881f5
--- /dev/null
+++ b/playground/rewrite-unoptimized/test-package/package.json
@@ -0,0 +1,6 @@
+{
+  "name": "rewrite-unoptimized-test-package",
+  "version": "1.0.0",
+  "main": "es/index.js",
+  "license": "MIT"
+}
diff --git a/playground/vite.config.ts b/playground/vite.config.ts
index f467b0073aa41a..f24c6f42d0e6ae 100644
--- a/playground/vite.config.ts
+++ b/playground/vite.config.ts
@@ -13,7 +13,7 @@ const config: UserConfig = {
   plugins: [jsPlugin],
   vueCustomBlockTransforms: { i18n: i18nTransform },
   optimizeDeps: {
-    exclude: ['bootstrap'],
+    exclude: ['bootstrap', 'rewrite-unoptimized-test-package'],
     link: ['optimize-linked']
   }
 }
diff --git a/playground/yarn.lock b/playground/yarn.lock
index 4f72d5f94f633f..712cf9a2947365 100644
--- a/playground/yarn.lock
+++ b/playground/yarn.lock
@@ -2,10 +2,18 @@
 # yarn lockfile v1
 
 
+"@babel/runtime@link:../node_modules/@babel/runtime":
+  version "0.0.0"
+  uid ""
+
 "bootstrap@link:../node_modules/bootstrap":
   version "0.0.0"
   uid ""
 
+"linked-dep@link:./optimize-linked/linked-dep":
+  version "0.0.0"
+  uid ""
+
 "lodash-es@link:../node_modules/lodash-es":
   version "0.0.0"
   uid ""
@@ -22,6 +30,11 @@
   version "0.0.0"
   uid ""
 
+regenerator-runtime@^0.13.4:
+  version "0.13.5"
+  resolved "https://registry.yarnpkg.com/regenerator-runtime/-/regenerator-runtime-0.13.5.tgz#d878a1d094b4306d10b9096484b33ebd55e26697"
+  integrity sha512-ZS5w8CpKFinUzOwW3c83oPeVXoNsrLsaCoLtJvAClH135j/R77RuymhiSErhm2lKcwSCIpmvIWSbDkIfAqKQlA==
+
 "resolve-browser-field-test-package@link:./resolve-browser-field":
   version "0.0.0"
   uid ""
@@ -29,3 +42,7 @@
 "rewrite-optimized-test-package@link:./rewrite-optimized/test-package":
   version "0.0.0"
   uid ""
+
+"rewrite-unoptimized-test-package@link:./rewrite-unoptimized/test-package":
+  version "0.0.0"
+  uid ""
diff --git a/src/node/resolver.ts b/src/node/resolver.ts
index 59011a7eb2a893..dfc0f05ab1c743 100644
--- a/src/node/resolver.ts
+++ b/src/node/resolver.ts
@@ -1,7 +1,13 @@
 import fs from 'fs-extra'
 import path from 'path'
 import slash from 'slash'
-import { cleanUrl, resolveFrom, queryRE } from './utils'
+import {
+  cleanUrl,
+  resolveFrom,
+  queryRE,
+  lookupFile,
+  parseNodeModuleId
+} from './utils'
 import {
   moduleRE,
   moduleIdToFileMap,
@@ -21,8 +27,8 @@ export interface Resolver {
 export interface InternalResolver {
   requestToFile(publicPath: string): string
   fileToRequest(filePath: string): string
+  normalizePublicPath(publicPath: string): string
   alias(id: string): string | undefined
-  resolveExt(publicPath: string): string | undefined
 }
 
 export const supportedExts = ['.mjs', '.js', '.ts', '.jsx', '.tsx', '.json']
@@ -70,26 +76,34 @@ const isFile = (file: string): boolean => {
   }
 }
 
-const resolveExt = (id: string): string | undefined => {
-  const cleanId = cleanUrl(id)
-  if (!isFile(cleanId)) {
-    let inferredExt = ''
+/**
+ * this function resolve fuzzy file path. examples:
+ * /path/file is a fuzzy file path for /path/file.tsx
+ * /path/dir is a fuzzy file path for /path/dir/index.js
+ *
+ * returning undefined indicates the filePath is not fuzzy:
+ * it is already an exact file path, or it can't match any file
+ */
+const resolveFilePathPostfix = (filePath: string): string | undefined => {
+  const cleanPath = cleanUrl(filePath)
+  if (!isFile(cleanPath)) {
+    let postfix = ''
     for (const ext of supportedExts) {
-      if (isFile(cleanId + ext)) {
-        inferredExt = ext
+      if (isFile(cleanPath + ext)) {
+        postfix = ext
         break
       }
-      if (isFile(path.join(cleanId, '/index' + ext))) {
-        inferredExt = '/index' + ext
+      if (isFile(path.join(cleanPath, '/index' + ext))) {
+        postfix = '/index' + ext
         break
       }
     }
-    const queryMatch = id.match(/\?.*$/)
+    const queryMatch = filePath.match(/\?.*$/)
     const query = queryMatch ? queryMatch[0] : ''
-    const resolved = cleanId + inferredExt + query
-    if (resolved !== id) {
-      debug(`(extension) ${id} -> ${resolved}`)
-      return inferredExt
+    const resolved = cleanPath + postfix + query
+    if (resolved !== filePath) {
+      debug(`(postfix) ${filePath} -> ${resolved}`)
+      return postfix
     }
   }
 }
@@ -141,51 +155,41 @@ export function createResolver(
   })
   resolveAlias(userAlias)
 
-  const requestToFileCache = new Map()
-  const fileToRequestCache = new Map()
-
-  const resolveRequest = (
-    publicPath: string
-  ): {
-    filePath: string
-    ext: string | undefined
-  } => {
-    if (requestToFileCache.has(publicPath)) {
-      return requestToFileCache.get(publicPath)
-    }
+  const requestToFileCache = new Map<string, string>()
+  const fileToRequestCache = new Map<string, string>()
 
-    let resolved: string | undefined
-    for (const r of resolvers) {
-      const filepath = r.requestToFile && r.requestToFile(publicPath, root)
-      if (filepath) {
-        resolved = filepath
-        break
-      }
-    }
-    if (!resolved) {
-      resolved = defaultRequestToFile(publicPath, root)
-    }
-    const ext = resolveExt(resolved)
-    const result = {
-      filePath: ext ? resolved + ext : resolved,
-      ext: ext || path.extname(resolved)
-    }
-    requestToFileCache.set(publicPath, result)
-    return result
-  }
-
-  return {
+  const resolver: InternalResolver = {
     requestToFile(publicPath) {
-      return resolveRequest(publicPath).filePath
-    },
+      if (requestToFileCache.has(publicPath)) {
+        return requestToFileCache.get(publicPath)!
+      }
 
-    resolveExt(publicPath) {
-      return resolveRequest(publicPath).ext
+      let resolved: string | undefined
+      for (const r of resolvers) {
+        const filepath = r.requestToFile && r.requestToFile(publicPath, root)
+        if (filepath) {
+          resolved = filepath
+          break
+        }
+      }
+      if (!resolved) {
+        resolved = defaultRequestToFile(publicPath, root)
+      }
+      const postfix = resolveFilePathPostfix(resolved)
+      if (postfix) {
+        if (postfix[0] === '/') {
+          resolved = path.join(resolved, postfix)
+        } else {
+          resolved += postfix
+        }
+      }
+      requestToFileCache.set(publicPath, resolved)
+      return resolved
     },
 
     fileToRequest(filePath) {
       if (fileToRequestCache.has(filePath)) {
-        return fileToRequestCache.get(filePath)
+        return fileToRequestCache.get(filePath)!
       }
       for (const r of resolvers) {
         const request = r.fileToRequest && r.fileToRequest(filePath, root)
@@ -196,6 +200,71 @@ export function createResolver(
       return res
     },
 
+    /**
+     * Given a fuzzy public path, resolve missing extensions and /index.xxx
+     */
+    normalizePublicPath(publicPath) {
+      // preserve query
+      const queryMatch = publicPath.match(/\?.*$/)
+      const query = queryMatch ? queryMatch[0] : ''
+      const cleanPublicPath = cleanUrl(publicPath)
+
+      const finalize = (result: string) => {
+        result += query
+        if (
+          resolver.requestToFile(result) !== resolver.requestToFile(publicPath)
+        ) {
+          throw new Error(
+            `[vite] normalizePublicPath check fail. please report to vite.`
+          )
+        }
+        return result
+      }
+
+      if (!moduleRE.test(cleanPublicPath)) {
+        return finalize(
+          resolver.fileToRequest(resolver.requestToFile(cleanPublicPath))
+        )
+      }
+
+      const filePath = resolver.requestToFile(cleanPublicPath)
+      const cacheDir = resolveOptimizedCacheDir(root)
+      if (cacheDir) {
+        const relative = path.relative(cacheDir, filePath)
+        if (!relative.startsWith('..')) {
+          return finalize(path.posix.join('/@modules/', slash(relative)))
+        }
+      }
+
+      // fileToRequest doesn't work with files in node_modules
+      // because of edge cases like symlinks or yarn-aliased-install
+      // or even aliased-symlinks
+
+      // example id: "@babel/runtime/helpers/esm/slicedToArray"
+      // see the test case: /playground/TestNormalizePublicPath.vue
+      const id = publicPath.replace(moduleRE, '')
+      const { scope, name, inPkgPath } = parseNodeModuleId(id)
+      if (!inPkgPath) return publicPath
+      let filePathPostFix = ''
+      let findPkgFrom = filePath
+      while (!filePathPostFix.startsWith(inPkgPath)) {
+        // some package contains multi package.json...
+        // for example: @babel/runtime@7.10.2/helpers/esm/package.json
+        const pkgPath = lookupFile(findPkgFrom, ['package.json'], true)
+        if (!pkgPath) {
+          throw new Error(
+            `[vite] can't find package.json for a node_module file: ` +
+              `"${publicPath}". something is wrong.`
+          )
+        }
+        filePathPostFix = slash(path.relative(path.dirname(pkgPath), filePath))
+        findPkgFrom = path.join(path.dirname(pkgPath), '../')
+      }
+      return finalize(
+        ['/@modules', scope, name, filePathPostFix].filter(Boolean).join('/')
+      )
+    },
+
     alias(id) {
       let aliased: string | undefined = literalAlias[id]
       if (aliased) {
@@ -210,6 +279,8 @@ export function createResolver(
       }
     }
   }
+
+  return resolver
 }
 
 export const jsSrcRE = /\.(?:(?:j|t)sx?|vue)$|\.mjs$/
@@ -371,10 +442,10 @@ export function resolveNodeModule(
     if (entryPoint) {
       // #284 some packages specify entry without extension...
       entryFilePath = path.join(path.dirname(pkgPath), entryPoint!)
-      const ext = resolveExt(entryFilePath)
-      if (ext) {
-        entryPoint += ext
-        entryFilePath += ext
+      const postfix = resolveFilePathPostfix(entryFilePath)
+      if (postfix) {
+        entryPoint += postfix
+        entryFilePath += postfix
       }
       entryPoint = path.posix.join(id, entryPoint!)
       // save the resolved file path now so we don't need to do it again in
diff --git a/src/node/server/serverPluginModuleRewrite.ts b/src/node/server/serverPluginModuleRewrite.ts
index 90c053b6f574df..7a5114195871cd 100644
--- a/src/node/server/serverPluginModuleRewrite.ts
+++ b/src/node/server/serverPluginModuleRewrite.ts
@@ -78,9 +78,7 @@ export const moduleRewritePlugin: ServerPlugin = ({
         // before we perform hmr analysis.
         // on the other hand, static import is guaranteed to have extension
         // because they must all have gone through module rewrite.
-        const importer = resolver.fileToRequest(
-          resolver.requestToFile(ctx.path)
-        )
+        const importer = resolver.normalizePublicPath(ctx.path)
         ctx.body = rewriteImports(
           root,
           content!,
@@ -254,11 +252,8 @@ export const resolveImport = (
     //    ./foo -> /some/path/foo
     let { pathname, query } = resolveRelativeRequest(importer, id)
 
-    // 2. resolve extensions.
-    const ext = resolver.resolveExt(pathname)
-    if (ext && ext !== path.extname(pathname)) {
-      pathname = path.posix.normalize(pathname + ext)
-    }
+    // 2. resolve dir index and extensions.
+    pathname = resolver.normalizePublicPath(pathname)
 
     // 3. mark non-src imports
     if (!query && path.extname(pathname) && !jsSrcRE.test(pathname)) {
diff --git a/src/node/utils/pathUtils.ts b/src/node/utils/pathUtils.ts
index 1478586684dea8..27e8b154d5fdba 100644
--- a/src/node/utils/pathUtils.ts
+++ b/src/node/utils/pathUtils.ts
@@ -74,3 +74,18 @@ export const isStaticAsset = (file: string) => {
 export const isImportRequest = (ctx: Context): boolean => {
   return ctx.query.import != null
 }
+
+export function parseNodeModuleId(id: string) {
+  const parts = id.split('/')
+  let scope = '',
+    name = '',
+    inPkgPath = ''
+  if (id.startsWith('@')) scope = parts.shift()!
+  name = parts.shift()!
+  inPkgPath = parts.join('/')
+  return {
+    scope,
+    name,
+    inPkgPath
+  }
+}
diff --git a/test/test.js b/test/test.js
index 42f676ae03cae0..df768cd5cbbab4 100644
--- a/test/test.js
+++ b/test/test.js
@@ -491,6 +491,10 @@ describe('vite', () => {
       )
     })
 
+    test('rewrite import in unoptimized deps', async () => {
+      expect(await getText('.test-rewrite-in-unoptimized')).toMatch('123')
+    })
+
     test('monorepo support', async () => {
       // linked dep + optimizing linked dep
       expect(await getText(`.optimize-linked`)).toMatch(`ok`)
@@ -516,6 +520,12 @@ describe('vite', () => {
         await expectByPolling(() => getText('.custom-block'), 'こんにちは')
       }
     })
+
+    test('normalize publicPath', async () => {
+      expect(await getText('.normalize-public-path')).toMatch(
+        JSON.stringify([2, 4])
+      )
+    })
   }
 
   // test build first since we are going to edit the fixtures when testing dev
diff --git a/yarn.lock b/yarn.lock
index 46f1fdb5cf25b6..996da4a545e00e 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -219,6 +219,13 @@
   dependencies:
     "@babel/helper-plugin-utils" "^7.8.0"
 
+"@babel/runtime@7.10.2":
+  version "7.10.2"
+  resolved "https://registry.yarnpkg.com/@babel/runtime/-/runtime-7.10.2.tgz#d103f21f2602497d38348a32e008637d506db839"
+  integrity sha512-6sF3uQw2ivImfVIl62RZ7MXhO2tap69WeWK57vAaimT6AZbE4FbqjdEJIN1UqoD6wI6B+1n9UiagafH1sxjOtg==
+  dependencies:
+    regenerator-runtime "^0.13.4"
+
 "@babel/runtime@^7.9.2":
   version "7.9.6"
   resolved "https://registry.yarnpkg.com/@babel/runtime/-/runtime-7.9.6.tgz#a9102eb5cadedf3f31d08a9ecf294af7827ea29f"