diff --git a/docker/README.md b/docker/README.md
index 267f02a31..bb0632533 100644
--- a/docker/README.md
+++ b/docker/README.md
@@ -20,6 +20,8 @@ The following env variables can be set to configure your Roundcube Docker instan
 
 `ROUNDCUBEMAIL_PLUGINS` - List of built-in plugins to activate. Defaults to `archive,zipdownload`
 
+`ROUNDCUBEMAIL_UPLOAD_MAX_FILESIZE` - File upload size limit; defaults to `5M`
+
 By default, the image will use a local SQLite database for storing user account metadata.
 It'll be created inside the `/var/www/html` volume and can be backed up from there. Please note that
 this option should not be used for production environments.
diff --git a/docker/docker-entrypoint.sh b/docker/docker-entrypoint.sh
index caa65adf8..a7d52946b 100755
--- a/docker/docker-entrypoint.sh
+++ b/docker/docker-entrypoint.sh
@@ -85,6 +85,10 @@ if [[ "$1" == apache2* ]] || [ "$1" == php-fpm ]; then
     echo "WARNING: $PWD/config/config.inc.php already exists."
     echo "ROUNDCUBEMAIL_* environment variables have been ignored."
   fi
+
+  if [ ! -z "${ROUNDCUBEMAIL_UPLOAD_MAX_FILESIZE}" ]; then
+    sed -i -E "s/(upload_max_filesize|post_max_size) +[0-9BKMG]+/\1 ${ROUNDCUBEMAIL_UPLOAD_MAX_FILESIZE}/g" $PWD/.htaccess
+  fi
 fi
 
 exec "$@"