diff --git a/.changeset/shy-seahorses-clean.md b/.changeset/shy-seahorses-clean.md
new file mode 100644
index 000000000..7fad0fbfc
--- /dev/null
+++ b/.changeset/shy-seahorses-clean.md
@@ -0,0 +1,5 @@
+---
+'astro': patch
+---
+
+Fixes cases where buildOptions.site is not respected
diff --git a/packages/astro/src/build/util.ts b/packages/astro/src/build/util.ts
index 9dc78b453..8314b9308 100644
--- a/packages/astro/src/build/util.ts
+++ b/packages/astro/src/build/util.ts
@@ -11,7 +11,11 @@ export function canonicalURL(url: string, base?: string): URL {
   pathname = pathname.replace(/\/1\/?$/, ''); // neither is a trailing /1/ (impl. detail of collections)
   if (!path.extname(pathname)) pathname = pathname.replace(/(\/+)?$/, '/'); // add trailing slash if there’s no extension
   pathname = pathname.replace(/\/+/g, '/'); // remove duplicate slashes (URL() won’t)
-  return new URL(pathname, base);
+  if(base) {
+    return new URL('.' + pathname, base);
+  } else {
+    return new URL(pathname, base);
+  }
 }
 
 /** Resolve final output URL */
diff --git a/packages/astro/src/compiler/index.ts b/packages/astro/src/compiler/index.ts
index b36384b83..27a3cf994 100644
--- a/packages/astro/src/compiler/index.ts
+++ b/packages/astro/src/compiler/index.ts
@@ -117,7 +117,7 @@ ${result.imports.join('\n')}
 
 ${/* Global Astro Namespace (shadowed & extended by the scoped namespace inside of __render()) */ ''}
 const __TopLevelAstro = {
-  site: new URL('/', ${JSON.stringify(site)}),
+  site: new URL(${JSON.stringify(site)}),
   fetchContent: (globResult) => fetchContent(globResult, import.meta.url),
 };
 const Astro = __TopLevelAstro;
diff --git a/packages/astro/src/runtime.ts b/packages/astro/src/runtime.ts
index acfa58400..8103d4bb9 100644
--- a/packages/astro/src/runtime.ts
+++ b/packages/astro/src/runtime.ts
@@ -68,8 +68,8 @@ async function load(config: RuntimeConfig, rawPathname: string | undefined): Pro
   const { logging, snowpackRuntime, snowpack, configManager } = config;
   const { buildOptions, devOptions } = config.astroConfig;
 
-  let origin = buildOptions.site ? new URL(buildOptions.site).origin : `http://${devOptions.hostname}:${devOptions.port}`;
-  const fullurl = new URL(rawPathname || '/', origin);
+  const site = new URL(buildOptions.site || `http://${devOptions.hostname}:${devOptions.port}`);
+  const fullurl = new URL(rawPathname || '/', site.origin);
 
   const reqPath = decodeURI(fullurl.pathname);
   info(logging, 'access', reqPath);
@@ -214,7 +214,7 @@ async function load(config: RuntimeConfig, rawPathname: string | undefined): Pro
       request: {
         // params should go here when implemented
         url: requestURL,
-        canonicalURL: canonicalURL(requestURL.pathname, requestURL.origin),
+        canonicalURL: canonicalURL(requestURL.pathname, site.toString()),
       },
       children: [],
       props: pageProps,
diff --git a/packages/astro/test/astro-global.test.js b/packages/astro/test/astro-global.test.js
index c6f5e47dd..3467cb738 100644
--- a/packages/astro/test/astro-global.test.js
+++ b/packages/astro/test/astro-global.test.js
@@ -18,10 +18,10 @@ Global('Astro.request.url', async (context) => {
 Global('Astro.request.canonicalURL', async (context) => {
   // given a URL, expect the following canonical URL
   const canonicalURLs = {
-    '/': 'https://mysite.dev/',
-    '/post/post': 'https://mysite.dev/post/post/',
-    '/posts': 'https://mysite.dev/posts/',
-    '/posts/2': 'https://mysite.dev/posts/2/',
+    '/': 'https://mysite.dev/blog/',
+    '/post/post': 'https://mysite.dev/blog/post/post/',
+    '/posts': 'https://mysite.dev/blog/posts/',
+    '/posts/2': 'https://mysite.dev/blog/posts/2/',
   };
 
   for (const [url, canonicalURL] of Object.entries(canonicalURLs)) {
@@ -36,7 +36,7 @@ Global('Astro.site', async (context) => {
   assert.ok(!result.error, `build error: ${result.error}`);
 
   const $ = doc(result.contents);
-  assert.equal($('#site').attr('href'), 'https://mysite.dev');
+  assert.equal($('#site').attr('href'), 'https://mysite.dev/blog/');
 });
 
 Global.run();
diff --git a/packages/astro/test/fixtures/astro-global/astro.config.mjs b/packages/astro/test/fixtures/astro-global/astro.config.mjs
index a618e1ba3..c601c31ad 100644
--- a/packages/astro/test/fixtures/astro-global/astro.config.mjs
+++ b/packages/astro/test/fixtures/astro-global/astro.config.mjs
@@ -1,6 +1,6 @@
 export default {
   buildOptions: {
-    site: 'https://mysite.dev',
+    site: 'https://mysite.dev/blog/',
     sitemap: false,
   },
 };
diff --git a/packages/astro/test/fixtures/astro-global/src/pages/index.astro b/packages/astro/test/fixtures/astro-global/src/pages/index.astro
index 43b0ee9a6..511f1bb3e 100644
--- a/packages/astro/test/fixtures/astro-global/src/pages/index.astro
+++ b/packages/astro/test/fixtures/astro-global/src/pages/index.astro
@@ -5,6 +5,6 @@
 </head>
 <body>
   <div id="pathname">{Astro.request.url.pathname}</div>
-  <a id="site" href={Astro.site.origin}>Home</a>
+  <a id="site" href={Astro.site}>Home</a>
 </body>
 </html>