diff --git a/Lodel/settings_format.py b/Lodel/settings_format.py
index 2f74f64..99c9cb1 100644
--- a/Lodel/settings_format.py
+++ b/Lodel/settings_format.py
@@ -19,4 +19,5 @@ MANDATORY = [
 ALLOWED = [
     'em_graph_output',
     'em_graph_format',
+    'templates_base_dir'
 ]
diff --git a/Template/Loader.py b/Template/Loader.py
index 98b7b43..620c19b 100644
--- a/Template/Loader.py
+++ b/Template/Loader.py
@@ -21,12 +21,13 @@ class TemplateLoader(object):
     # @param template_file str : path to the template file (starting from the base path used to instanciate the
     #                            TemplateLoader)
     # @param template_vars dict : parameters to be used in the template
+    # @param template_extra list : list of custom modules to import in the template (default value : None)
     # @return str. String containing the HTML output of the processed templated
-    def render_to_html(self, template_file, template_vars={}, template_extra={}):
+    def render_to_html(self, template_file, template_vars={}, template_extra=None):
         loader = jinja2.FileSystemLoader(searchpath=self.search_path, followlinks=self.follow_links)
         environment = jinja2.Environment(loader=loader)
         template = environment.get_template(template_file)
-        if template_extra is not None or template_extra != {}:
+        if template_extra is not None:
             for extra in template_extra:
                 template.globals[extra[0]] = extra[1]
         return template.render(template_vars)
diff --git a/install/instance_settings.py b/install/instance_settings.py
index 476a227..e61d4d3 100644
--- a/install/instance_settings.py
+++ b/install/instance_settings.py
@@ -1,10 +1,13 @@
 #-*- coding:utf8 -*-
 
 import pymysql
+import os
 
 sitename = 'LODEL2_INSTANCE_NAME'
 lodel2_lib_path = 'LODEL2_LIB_ABS_PATH'
 
+templates_base_dir = 'LODEL2_INSTANCE_TEMPLATES_BASE_DIR'
+
 debug = False
 
 em_file = 'em.json'