diff --git a/packages/next/client/page-loader.js b/packages/next/client/page-loader.js
index c2960466e5567..9f54bd70ea8c9 100644
--- a/packages/next/client/page-loader.js
+++ b/packages/next/client/page-loader.js
@@ -109,17 +109,18 @@ export default class PageLoader {
    * @param {string} href the route href (file-system path)
    * @param {string} asPath the URL as shown in browser (virtual path); used for dynamic routes
    */
-  getDataHref(href, asPath) {
+  getDataHref(href, asPath, ssg) {
+    const { pathname: hrefPathname, query, search } = parse(href, true)
+    const { pathname: asPathname } = parse(asPath)
+    const route = normalizeRoute(hrefPathname)
+
     const getHrefForSlug = (/** @type string */ path) => {
       const dataRoute = getAssetPathFromRoute(path, '.json')
-      return `${this.assetPrefix}/_next/data/${this.buildId}${dataRoute}`
+      return `${this.assetPrefix}/_next/data/${this.buildId}${dataRoute}${
+        ssg ? '' : search || ''
+      }`
     }
 
-    const { pathname: hrefPathname, query } = parse(href, true)
-    const { pathname: asPathname } = parse(asPath)
-
-    const route = normalizeRoute(hrefPathname)
-
     let isDynamic = isDynamicRoute(route),
       interpolatedRoute
     if (isDynamic) {
@@ -135,19 +136,19 @@ export default class PageLoader {
       interpolatedRoute = route
       if (
         !Object.keys(dynamicGroups).every((param) => {
-          let value = dynamicMatches[param]
+          let value = dynamicMatches[param] || ''
           const { repeat, optional } = dynamicGroups[param]
 
           // support single-level catch-all
           // TODO: more robust handling for user-error (passing `/`)
-          if (repeat && !Array.isArray(value)) value = [value]
           let replaced = `[${repeat ? '...' : ''}${param}]`
           if (optional) {
-            replaced = `[${replaced}]`
+            replaced = `${!value ? '/' : ''}[${replaced}]`
           }
+          if (repeat && !Array.isArray(value)) value = [value]
 
           return (
-            param in dynamicMatches &&
+            (optional || param in dynamicMatches) &&
             // Interpolate group into data URL if present
             (interpolatedRoute = interpolatedRoute.replace(
               replaced,
@@ -182,7 +183,7 @@ export default class PageLoader {
         // Check if the route requires a data file
         s.has(route) &&
         // Try to generate data href, noop when falsy
-        (_dataHref = this.getDataHref(href, asPath)) &&
+        (_dataHref = this.getDataHref(href, asPath, true)) &&
         // noop when data has already been prefetched (dedupe)
         !document.querySelector(
           `link[rel="${relPrefetch}"][href^="${_dataHref}"]`
diff --git a/packages/next/next-server/lib/router/router.ts b/packages/next/next-server/lib/router/router.ts
index 2acfa7fcd089a..e92e603d4414b 100644
--- a/packages/next/next-server/lib/router/router.ts
+++ b/packages/next/next-server/lib/router/router.ts
@@ -16,7 +16,6 @@ import { isDynamicRoute } from './utils/is-dynamic'
 import { getRouteMatcher } from './utils/route-matcher'
 import { getRouteRegex } from './utils/route-regex'
 import { normalizeTrailingSlash } from './normalize-trailing-slash'
-import getAssetPathFromRoute from './utils/get-asset-path-from-route'
 
 const basePath = (process.env.__NEXT_ROUTER_BASEPATH as string) || ''
 
@@ -108,39 +107,26 @@ type ComponentLoadCancel = (() => void) | null
 type HistoryMethod = 'replaceState' | 'pushState'
 
 function fetchNextData(
-  pathname: string,
-  query: ParsedUrlQuery | null,
+  dataHref: string,
   isServerRender: boolean,
   cb?: (...args: any) => any
 ) {
   let attempts = isServerRender ? 3 : 1
   function getResponse(): Promise<any> {
-    return fetch(
-      formatWithValidation({
-        pathname: addBasePath(
-          // @ts-ignore __NEXT_DATA__
-          `/_next/data/${__NEXT_DATA__.buildId}${getAssetPathFromRoute(
-            pathname,
-            '.json'
-          )}`
-        ),
-        query,
-      }),
-      {
-        // Cookies are required to be present for Next.js' SSG "Preview Mode".
-        // Cookies may also be required for `getServerSideProps`.
-        //
-        // > `fetch` won’t send cookies, unless you set the credentials init
-        // > option.
-        // https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API/Using_Fetch
-        //
-        // > For maximum browser compatibility when it comes to sending &
-        // > receiving cookies, always supply the `credentials: 'same-origin'`
-        // > option instead of relying on the default.
-        // https://github.com/github/fetch#caveats
-        credentials: 'same-origin',
-      }
-    ).then((res) => {
+    return fetch(dataHref, {
+      // Cookies are required to be present for Next.js' SSG "Preview Mode".
+      // Cookies may also be required for `getServerSideProps`.
+      //
+      // > `fetch` won’t send cookies, unless you set the credentials init
+      // > option.
+      // https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API/Using_Fetch
+      //
+      // > For maximum browser compatibility when it comes to sending &
+      // > receiving cookies, always supply the `credentials: 'same-origin'`
+      // > option instead of relying on the default.
+      // https://github.com/github/fetch#caveats
+      credentials: 'same-origin',
+    }).then((res) => {
       if (!res.ok) {
         if (--attempts > 0 && res.status >= 500) {
           return getResponse()
@@ -669,11 +655,21 @@ export default class Router implements BaseRouter {
           }
         }
 
+        let dataHref: string | undefined
+
+        if (__N_SSG || __N_SSP) {
+          dataHref = this.pageLoader.getDataHref(
+            formatWithValidation({ pathname, query }),
+            as,
+            __N_SSG
+          )
+        }
+
         return this._getData<RouteInfo>(() =>
           __N_SSG
-            ? this._getStaticData(as)
+            ? this._getStaticData(dataHref!)
             : __N_SSP
-            ? this._getServerData(as)
+            ? this._getServerData(dataHref!)
             : this.getInitialProps(
                 Component,
                 // we provide AppTree later so this needs to be `any`
@@ -843,23 +839,20 @@ export default class Router implements BaseRouter {
     })
   }
 
-  _getStaticData = (asPath: string): Promise<object> => {
-    const pathname = prepareRoute(parse(asPath).pathname!)
+  _getStaticData = (dataHref: string): Promise<object> => {
+    const pathname = prepareRoute(parse(dataHref).pathname!)
 
     return process.env.NODE_ENV === 'production' && this.sdc[pathname]
-      ? Promise.resolve(this.sdc[pathname])
+      ? Promise.resolve(this.sdc[dataHref])
       : fetchNextData(
-          pathname,
-          null,
+          dataHref,
           this.isSsr,
           (data) => (this.sdc[pathname] = data)
         )
   }
 
-  _getServerData = (asPath: string): Promise<object> => {
-    let { pathname, query } = parse(asPath, true)
-    pathname = prepareRoute(pathname!)
-    return fetchNextData(pathname, query, this.isSsr)
+  _getServerData = (dataHref: string): Promise<object> => {
+    return fetchNextData(dataHref, this.isSsr)
   }
 
   getInitialProps(
diff --git a/test/integration/build-output/test/index.test.js b/test/integration/build-output/test/index.test.js
index 8064d3aa323b7..efa0151d49045 100644
--- a/test/integration/build-output/test/index.test.js
+++ b/test/integration/build-output/test/index.test.js
@@ -113,7 +113,7 @@ describe('Build Output', () => {
       expect(parseFloat(webpackSize) - 775).toBeLessThanOrEqual(0)
       expect(webpackSize.endsWith('B')).toBe(true)
 
-      expect(parseFloat(mainSize) - 6.3).toBeLessThanOrEqual(0)
+      expect(parseFloat(mainSize) - 6.4).toBeLessThanOrEqual(0)
       expect(mainSize.endsWith('kB')).toBe(true)
 
       expect(parseFloat(frameworkSize) - 41).toBeLessThanOrEqual(0)
diff --git a/test/integration/prerender/pages/index.js b/test/integration/prerender/pages/index.js
index 240a501befd50..ac34b844f7016 100644
--- a/test/integration/prerender/pages/index.js
+++ b/test/integration/prerender/pages/index.js
@@ -52,6 +52,10 @@ const Page = ({ world, time }) => {
         <a id="to-nested-index">to nested index</a>
       </Link>
       <br />
+      <Link href="/lang/[lang]/about?lang=en" as="/about">
+        <a id="to-rewritten-ssg">to rewritten static path page</a>
+      </Link>
+      <br />
       <Link href="/catchall-optional/[[...slug]]" as="/catchall-optional">
         <a id="catchall-optional-root">to optional catchall root</a>
       </Link>
diff --git a/test/integration/prerender/pages/lang/[lang]/about.js b/test/integration/prerender/pages/lang/[lang]/about.js
index 693a814883c73..a985dea17b0a9 100644
--- a/test/integration/prerender/pages/lang/[lang]/about.js
+++ b/test/integration/prerender/pages/lang/[lang]/about.js
@@ -1,4 +1,4 @@
-export default ({ lang }) => <p>About: {lang}</p>
+export default ({ lang }) => <p id="about">About: {lang}</p>
 
 export const getStaticProps = ({ params: { lang } }) => ({
   props: {
diff --git a/test/integration/prerender/test/index.test.js b/test/integration/prerender/test/index.test.js
index 52c36ce6854c8..23f5c8283149c 100644
--- a/test/integration/prerender/test/index.test.js
+++ b/test/integration/prerender/test/index.test.js
@@ -25,6 +25,7 @@ import {
 } from 'next-test-utils'
 import webdriver from 'next-webdriver'
 import { dirname, join } from 'path'
+import url from 'url'
 
 jest.setTimeout(1000 * 60 * 2)
 const appDir = join(__dirname, '..')
@@ -601,6 +602,45 @@ const runTests = (dev = false, isEmulatedServerless = false) => {
       const html = await renderViaHTTP(appPort, '/about')
       expect(html).toMatch(/About:.*?en/)
     })
+
+    it('should fetch /_next/data correctly with mismatched href and as', async () => {
+      const browser = await webdriver(appPort, '/')
+
+      if (!dev) {
+        await browser.eval(() =>
+          document.querySelector('#to-rewritten-ssg').scrollIntoView()
+        )
+
+        await check(
+          async () => {
+            const links = await browser.elementsByCss('link[rel=prefetch]')
+            let found = false
+
+            for (const link of links) {
+              const href = await link.getAttribute('href')
+              const { pathname } = url.parse(href)
+
+              if (pathname.endsWith('/lang/en/about.json')) {
+                found = true
+                break
+              }
+            }
+            return found
+          },
+          {
+            test(result) {
+              return result === true
+            },
+          }
+        )
+      }
+      await browser.eval('window.beforeNav = "hi"')
+      await browser.elementByCss('#to-rewritten-ssg').click()
+      await browser.waitForElementByCss('#about')
+
+      expect(await browser.eval('window.beforeNav')).toBe('hi')
+      expect(await browser.elementByCss('#about').text()).toBe('About: en')
+    })
   }
 
   if (dev) {