diff --git a/.env.dist b/.env.dist
index f663a86..63a5121 100644
--- a/.env.dist
+++ b/.env.dist
@@ -64,8 +64,10 @@ PLEROMA_VERSION=develop
 # The domain/scheme where pleroma will be hosted
 # URL is a bare TLD
 # SCHEME is the protocol without "://"
+# PORT is the *external* port (ie that of your reverse proxy)
 PLEROMA_URL=example.com
 PLEROMA_SCHEME=https
+PLEROMA_PORT=443
 
 # The seed for your secret keys
 # (Enter something as random as possible)
diff --git a/docker-compose.m4 b/docker-compose.m4
index bfea23c..f900403 100644
--- a/docker-compose.m4
+++ b/docker-compose.m4
@@ -102,6 +102,7 @@ define(<env_inline_fb>, <${upcase($1):-$2}>)
 
         "env(<pleroma_url>)",
         "env(<pleroma_scheme>)",
+        "env(<pleroma_port>)",
         "env(<pleroma_secret_key_base>)",
         "env(<pleroma_name>)",
         "env(<pleroma_admin_email>)",
diff --git a/docker-config.exs b/docker-config.exs
index 9290bb9..114dbc2 100644
--- a/docker-config.exs
+++ b/docker-config.exs
@@ -18,7 +18,7 @@ config :pleroma, Pleroma.Web.Endpoint,
     url: [
         host: Docker.env(:url),
         scheme: Docker.env(:scheme),
-        port: 4000
+        port: Docker.env(:port)
     ],
     secret_key_base: Docker.env(:secret_key_base)