diff --git a/Dockerfile b/Dockerfile
index ea1c76b..1b3c3e6 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -46,7 +46,7 @@ COPY run.sh /usr/local/bin/run.sh
 
 RUN chmod +x /usr/local/bin/* /etc/s6.d/*/* /etc/s6.d/.s6-svscan/*
 
-VOLUME /flarum/app/assets
+VOLUME /flarum/app/assets /flarum/app/extensions
 
 EXPOSE 8888
 
diff --git a/README.md b/README.md
index bfe928d..20e16c3 100644
--- a/README.md
+++ b/README.md
@@ -66,7 +66,8 @@ flarum:
     - FORUM_URL=https://forum.domain.tld
     - DB_PASS=xxxxxxxx
   volumes:
-    - /mnt/docker/flarum:/flarum/app/assets
+    - /mnt/docker/flarum/assets:/flarum/app/assets
+    - /mnt/docker/flarum/extensions:/flarum/app/extensions
 
 mariadb:
   image: mariadb:10.1
@@ -136,66 +137,24 @@ docker exec -ti flarum extension list
 
 ### Custom error pages
 
-To use custom error pages, add your .html files in `/mnt/docker/flarum/errors` folder :
+To use custom error pages, add your .html files in `/mnt/docker/flarum/assets/errors` folder :
 
 ```
-mkdir -p /mnt/docker/flarum/errors
+mkdir -p /mnt/docker/flarum/assets/errors
 touch 403.html 404.html 500.html 503.html
 chown -R 991:991 /mnt/docker/flarum
 ```
 
-### Custom composer.json (experienced users)
+### Custom composer repositories
 
-Customize your own composer.json file in `/mnt/docker/flarum/composer.custom.json`, for example add some privates repositories like this :
+To use the composer repository system, add your repo name and json representation in `/mnt/docker/flarum/extensions/composer.repositories.txt` :
 
-```json
-# /mnt/docker/flarum/composer.custom.json
-{
-  "name": "flarum/flarum",
-  "description": "Delightfully simple forum software.",
-  [...]
-
-  "repositories": [
-    {
-      "type": "package",
-      "package": {
-        "name": "xxxxx/flarum-ext-my-private-extension",
-        "version": "dev-master",
-        "type": "flarum-extension",
-        "authors": [
-          {
-            "name": "Me",
-            "email": "me@domain.tld"
-          }
-        ],
-        "dist": {
-          "url": "/flarum/app/assets/extensions/flarum-ext-my-private-extension",
-          "type": "path",
-          "reference": "master"
-        },
-        "require": {
-          "flarum/core": "^0.1.0-beta.6"
-        },
-        "autoload": {
-          "psr-4": {
-            "xxx\\xxx\\": "src/"
-          }
-        },
-        "extra": {
-          "flarum-extension": {
-            "title": "xxxxxx",
-            "icon": {
-              "name": "picture-o",
-              "backgroundColor": "#2196f3",
-              "color": "#fff"
-            }
-          }
-        }
-      }
-    }
-  ],
-}
 ```
+my_private_repo|{"type":"path","url":"extensions/*/"}
+my_public_repo|{"type":"vcs","url":"https://github.com/my/repo"}
+```
+
+https://getcomposer.org/doc/03-cli.md#modifying-repositories
 
 ### Screenshot
 
diff --git a/extension b/extension
index 3eb0b2e..3dccbfb 100644
--- a/extension
+++ b/extension
@@ -9,8 +9,8 @@ CRED="${CSI}1;31m"
 CGREEN="${CSI}1;32m"
 
 # Composer cache dir and packages list paths
-CACHE_DIR=/flarum/app/assets/.extensions
-LIST_FILE=assets/.extensions/list
+CACHE_DIR=extensions/.cache
+LIST_FILE=extensions/list
 
 # Cmd ARGS
 action=$1
@@ -55,4 +55,6 @@ case "$action" in
     ;;
 esac
 
+su-exec $UID:$GID php flarum cache:clear
+
 exit 0
diff --git a/run.sh b/run.sh
index 0a4ad5d..36c6400 100644
--- a/run.sh
+++ b/run.sh
@@ -30,13 +30,19 @@ cd /flarum/app
 
 # Custom HTTP errors pages
 if [ -d 'assets/errors' ]; then
+  echo "[INFO] Found custom errors pages"
   rm -rf vendor/flarum/core/error/*
   ln -s /flarum/app/assets/errors/* vendor/flarum/core/error
 fi
 
-# Custom composer.json (eg. for privates extensions)
-if [ -f 'assets/composer.custom.json' ]; then
-  cp -f assets/composer.custom.json composer.json
+# Custom repositories (eg. for privates extensions)
+if [ -f 'extensions/composer.repositories.txt' ]; then
+  while read line; do
+    repository=$(echo $line | cut -d '|' -f1)
+    json=$(echo $line | cut -d '|' -f2)
+    echo "[INFO] Adding ${repository} composer repository"
+    composer config repositories.${repository} "${json}"
+  done < extensions/composer.repositories.txt
 fi
 
 # if no installation was performed before
@@ -55,8 +61,8 @@ if [ -e 'assets/rev-manifest.json' ]; then
   su-exec $UID:$GID php flarum cache:clear
 
   # Composer cache dir and packages list paths
-  CACHE_DIR=assets/.extensions
-  LIST_FILE=$CACHE_DIR/list
+  CACHE_DIR=extensions/.cache
+  LIST_FILE=extensions/list
 
   # Download extra extensions installed with composer wrapup script
   if [ -s "$LIST_FILE" ]; then