diff --git a/ahserver/processorResource.py b/ahserver/processorResource.py
index bf942cf..a625a94 100755
--- a/ahserver/processorResource.py
+++ b/ahserver/processorResource.py
@@ -384,15 +384,17 @@ class ProcessorResource(AppLogger, StaticResource,Url2File):
 			return url
 		scheme = request.headers.get('X-Forwarded-Scheme') or request.scheme
 		port = request.headers.get('X-Forwarded-Port') or str(request['port'])
+		prepath = request.headers.get('X-Forwarded-Prepath') or ''
+		if prepath != '':
+			prepath = f'/{prepath}'
 		h = self.gethost(request)
 		if url.startswith('/'):
-			return f'{scheme}://{h}:{port}{url}'
+			return f'{scheme}://{h}:{port}{url}{prepath}'
 		path = request.path
 		if self.request_filename and os.path.isdir(self.request_filename):
 			path = '%s/oops' % path
 		p = self.relatedurl(path,url)
-		return f'{scheme}://{h}:{port}{p}'
-		return '%s://%s:%s%s' % (scheme, h, port, p)
+		return f'{scheme}://{h}:{port}{prepath}{p}'
 
 	async def path_call(self, request, path, params={}):
 		url = self.entireUrl(request, path)