diff --git a/routes/proxy-route.ts b/routes/proxy-route.ts
index 1ba7eb69..31109545 100644
--- a/routes/proxy-route.ts
+++ b/routes/proxy-route.ts
@@ -60,7 +60,7 @@ export function proxyRoute(options: ProxyRouteOptions): HTTPMiddleware {
       let body = yield* call(() => response.text());
       let tree = fromHtml(body);
 
-      let elements = selectAll('[href^="/"],[src^="/"]', tree);
+      let elements = selectAll('[href^="/"],[src^="/"],form[action]', tree);
 
       for (let element of elements) {
         let properties = element.properties!;
@@ -73,6 +73,11 @@ export function proxyRoute(options: ProxyRouteOptions): HTTPMiddleware {
         if (properties.src) {
           properties.src = posixNormalize(`${base.pathname}${properties.src}`);
         }
+        if (properties.action) {
+          properties.action = posixNormalize(
+            `${base.pathname}${properties.action}`,
+          );
+        }
       }
       let headers: Record<string, string> = {};
       for (let [key, value] of response.headers.entries()) {