diff --git a/scripts/_common.sh b/scripts/_common.sh
index a862ce1..9a7d810 100644
--- a/scripts/_common.sh
+++ b/scripts/_common.sh
@@ -7,6 +7,9 @@
 # nodejs version
 nodejs_version=16
 
+# Terraforming-mars commit
+TM_version="a36d327"
+
 #=================================================
 # PERSONAL HELPERS
 #=================================================
diff --git a/scripts/install b/scripts/install
index 55db793..d573b19 100755
--- a/scripts/install
+++ b/scripts/install
@@ -19,19 +19,6 @@ ynh_exec_warn_less ynh_install_nodejs --nodejs_version=$nodejs_version
 # Upgrade NPM
 ynh_npm install --global npm@6.14.18
 
-
-#=================================================
-# DOWNLOAD, CHECK AND UNPACK SOURCE
-#=================================================
-ynh_script_progression --message="Setting up source files..." --weight=1
-
-# Download, check integrity, uncompress and patch the source from app.src
-#ynh_setup_source --dest_dir="$install_dir"
-
-chmod 750 "$install_dir"
-chmod -R o-rwx "$install_dir"
-chown -R $app:www-data "$install_dir"
-
 #=================================================
 # NGINX CONFIGURATION
 #=================================================
@@ -48,7 +35,8 @@ ynh_add_nginx_config
 #=================================================
 
 cd $install_dir
-git clone https://github.com/terraforming-mars/terraforming-mars.git
+ynh_exec_warn_less git clone https://github.com/terraforming-mars/terraforming-mars.git
+git checkout $TM_version
 
 pushd $install_dir/terraforming-mars
     ynh_use_nodejs
diff --git a/scripts/upgrade b/scripts/upgrade
index e36bba5..0007687 100755
--- a/scripts/upgrade
+++ b/scripts/upgrade
@@ -30,35 +30,23 @@ ynh_npm install --global npm@6.14.18
 
 #=================================================
 # "REBUILD" THE APP (DEPLOY NEW SOURCES, RERUN NPM BUILD...)
-#=================================================
-# DOWNLOAD, CHECK AND UNPACK SOURCE
-#=================================================
-ynh_script_progression --message="Setting up source files..." --weight=1
-	
-# Download, check integrity, uncompress and patch the source from app.src
-ynh_setup_source --dest_dir="$install_dir" --full-replace=1
-
-chmod 750 "$install_dir"
-chmod -R o-rwx "$install_dir"
-chown -R $app:www-data "$install_dir"
-
 #=================================================
 # BUILD APP
 #=================================================
 ynh_script_progression --message="Building app... This may take quiete some time" --weight=30
 
-pushd $install_dir
+cd $install_dir
+ynh_exec_warn_less git clone https://github.com/terraforming-mars/terraforming-mars.git
+git checkout $TM_version
+
+pushd $install_dir/terraforming-mars
     ynh_use_nodejs
 
-	ynh_script_progression --message="Fetching Yarn dev dependencies... This can be very long, be patient !" --weight=18
-	ynh_exec_warn_less ynh_exec_as $app env $ynh_node_load_PATH yarn install --network-timeout=100000
-
-	ynh_script_progression --message="Building Yarn dev dependencies... This can be very long, be patient !" --weight=25
-	ynh_exec_warn_less ynh_exec_as $app env $ynh_node_load_PATH yarn run build
-	
-	ynh_script_progression --message="Cleaning cache... " --weight=3
-	ynh_exec_warn_less sudo -u $app env $ynh_node_load_PATH yarn cache clean 2>&1
+	ynh_script_progression --message="npm install... This can be very long, be patient !" --weight=18
+	ynh_exec_warn_less env $ynh_node_load_PATH $ynh_npm install --network-timeout=100000
 
+	ynh_script_progression --message="npm run build... This can be very long, be patient !" --weight=25
+	ynh_exec_warn_less env $ynh_node_load_PATH $ynh_npm run build
 popd
 
 chmod 750 "$install_dir"