diff --git a/src/node/app/proxy.ts b/src/node/app/proxy.ts
index e069d2e60..7b79d96f6 100644
--- a/src/node/app/proxy.ts
+++ b/src/node/app/proxy.ts
@@ -61,7 +61,9 @@ export class ProxyHttpProvider extends HttpProvider implements HttpProxyProvider
         current = domain
       }
     })
-    return current || host
+    // Setting the domain to localhost doesn't seem to work for subdomains (for
+    // example dev.localhost).
+    return current && current !== "localhost" ? current : host
   }
 
   public maybeProxyRequest(
@@ -90,12 +92,11 @@ export class ProxyHttpProvider extends HttpProvider implements HttpProxyProvider
       return undefined
     }
 
-    // At minimum there needs to be sub.domain.tld.
-    const host = request.headers.host
-    const parts = host && host.split(".")
-    if (!parts || parts.length < 3) {
-      return undefined
-    }
+    // Split into parts.
+    const host = request.headers.host || ""
+    const idx = host.indexOf(":")
+    const domain = idx !== -1 ? host.substring(0, idx) : host
+    const parts = domain.split(".")
 
     // There must be an exact match.
     const port = parts.shift()
diff --git a/src/node/http.ts b/src/node/http.ts
index 5b62eef6a..525033080 100644
--- a/src/node/http.ts
+++ b/src/node/http.ts
@@ -581,6 +581,9 @@ export class HttpServer {
     this.heart.beat()
     const route = this.parseUrl(request)
     const write = (payload: HttpResponse): void => {
+      const host = request.headers.host || ""
+      const idx = host.indexOf(":")
+      const domain = idx !== -1 ? host.substring(0, idx) : host
       response.writeHead(payload.redirect ? HttpCode.Redirect : payload.code || HttpCode.Ok, {
         "Content-Type": payload.mime || getMediaMime(payload.filePath),
         ...(payload.redirect ? { Location: this.constructRedirect(request, route, payload as RedirectResponse) } : {}),
@@ -591,9 +594,7 @@ export class HttpServer {
               "Set-Cookie": [
                 `${payload.cookie.key}=${payload.cookie.value}`,
                 `Path=${normalize(payload.cookie.path || "/", true)}`,
-                request.headers.host
-                  ? `Domain=${(this.proxy && this.proxy.getCookieDomain(request.headers.host)) || request.headers.host}`
-                  : undefined,
+                domain ? `Domain=${(this.proxy && this.proxy.getCookieDomain(domain)) || domain}` : undefined,
                 // "HttpOnly",
                 "SameSite=strict",
               ]