diff --git a/mitmproxy/proxy/protocol/http.py b/mitmproxy/proxy/protocol/http.py
index acc848e18..726ed2c7a 100644
--- a/mitmproxy/proxy/protocol/http.py
+++ b/mitmproxy/proxy/protocol/http.py
@@ -8,6 +8,7 @@ from mitmproxy import connections  # noqa
 from mitmproxy import exceptions
 from mitmproxy import http
 from mitmproxy import flow
+from mitmproxy.net.http import url
 from mitmproxy.proxy.protocol import base
 from mitmproxy.proxy.protocol.websocket import WebSocketLayer
 from mitmproxy.net import websocket
@@ -326,7 +327,10 @@ class HttpLayer(base.Layer):
 
         # update host header in reverse proxy mode
         if self.config.options.mode.startswith("reverse:") and not self.config.options.keep_host_header:
-            f.request.host_header = self.config.upstream_server.address[0]
+            f.request.host_header = url.hostport(
+                self.config.upstream_server.scheme,
+                *self.config.upstream_server.address
+            )
 
         # Determine .scheme, .host and .port attributes for inline scripts. For
         # absolute-form requests, they are directly given in the request. For
diff --git a/test/mitmproxy/proxy/test_server.py b/test/mitmproxy/proxy/test_server.py
index 03e68e856..d092f73e5 100644
--- a/test/mitmproxy/proxy/test_server.py
+++ b/test/mitmproxy/proxy/test_server.py
@@ -452,7 +452,7 @@ class TestReverse(tservers.ReverseProxyTest, CommonMixin, TcpMixin):
         assert resp.status_code == 200
 
         req = self.master.state.flows[0].request
-        assert req.host_header == "127.0.0.1"
+        assert req.host_header.startswith("127.0.0.1:")
 
     @pytest.mark.asyncio
     async def test_selfconnection(self):