diff --git a/.changeset/wild-ducks-decide.md b/.changeset/wild-ducks-decide.md
new file mode 100644
index 0000000000..8a6f85be73
--- /dev/null
+++ b/.changeset/wild-ducks-decide.md
@@ -0,0 +1,5 @@
+---
+'@astrojs/upgrade': patch
+---
+
+Fixes a bug that caused registry URLs that specify a port to be incorrectly detected as offline.
diff --git a/packages/upgrade/src/actions/verify.ts b/packages/upgrade/src/actions/verify.ts
index 384df5134a..3b7c15a9e1 100644
--- a/packages/upgrade/src/actions/verify.ts
+++ b/packages/upgrade/src/actions/verify.ts
@@ -43,8 +43,8 @@ export async function verify(
 }
 
 function isOnline(registry: string): Promise<boolean> {
-	const { host } = new URL(registry);
-	return dns.lookup(host).then(
+	const { hostname } = new URL(registry);
+	return dns.lookup(hostname).then(
 		() => true,
 		() => false,
 	);