diff --git a/README.md b/README.md
index 6207481..60f0fea 100644
--- a/README.md
+++ b/README.md
@@ -421,7 +421,43 @@ documentation.
 
 Such customized functions must accept parameters explicilty, otherwise `sass_processor` does not
 know how to map them. Variable argument lists therefore can not be used.
+Starting from the fact that libsass can not use the custom_functions in a list scss natively. An action has been implemented to overcome this and concerns only the source sass_src file.
 
+The conditions are as follows:
++ the name of the function must have "presass" in its name.
++ must not have args in parameter.
+
+Its operation is as follows:
+```
+{% addtoblock "css" %}<link rel="stylesheet" href="{% sass_src 'bs4demo/css/main.scss' %}" type="text/css" />{% endaddtoblock %}
+```
+From the main.scss files, a main__presass.scss file is created which has hard values in the files.
+Then, to check if main.scss has been modified, the file css.map is scrapper to restore its source origin.
+
+Example: 
+settings.py
+```
+SASS_PROCESSOR_CUSTOM_FUNCTIONS = {
+    'get-color-primary-presass': 'cmsplugin_cascade.theme.utils.get_color_primary',
+    'get-color-secondary-presass': 'cmsplugin_cascade.theme.utils.get_color_secondary',
+    'get-color-success-presass': 'cmsplugin_cascade.theme.utils.get_color_success',
+    'get-color-warning-presass': 'cmsplugin_cascade.theme.utils.get_color_warning',
+    'get-color-danger-presass': 'cmsplugin_cascade.theme.utils.get_color_danger',
+    'get-color-info-presass': 'cmsplugin_cascade.theme.utils.get_color_info',
+    'get-color-light-presass': 'cmsplugin_cascade.theme.utils.get_color_light',
+    'get-color-dark-presass': 'cmsplugin_cascade.theme.utils.get_color_dark',
+}
+```
+
+main.scss:
+```
+@import "variables";
+$theme-colors: (
+ primary: get-color-primary-presass()
+);
+@import "bootstrap/scss/bootstrap";
+@import "footer";
+```
 
 ## Error reporting
 
diff --git a/sass_processor/processor.py b/sass_processor/processor.py
index 0d80914..8d04168 100644
--- a/sass_processor/processor.py
+++ b/sass_processor/processor.py
@@ -72,8 +72,28 @@ def __call__(self, path):
 
         # otherwise compile the SASS/SCSS file into .css and store it
         filename_map = filename.replace(ext, '.css.map')
+
+        # 1 fake custom_function in list for only master source scss
+        custom_function_presass = {}
+        for custom_function in get_custom_functions() :
+            #check if tuple index out of range
+            if 'presass' in custom_function.name: 
+                custom_function_presass.update({ custom_function.name :custom_function() })
+        filename_scss = filename.replace(ext, '__presass.scss')
+        with open(filename, "rt") as fin:
+            with open(filename_scss , "wt") as fout:
+                for line in fin:
+                    linem = None
+                    for key , value in custom_function_presass.items():
+                        if key in line: 
+                            linem = line.replace('{}{}'.format(key, '()'), value)
+                    if linem:
+                        fout.write(linem)
+                    else:
+                        fout.write(line)
+
         compile_kwargs = {
-            'filename': filename,
+            'filename': filename_scss,
             'source_map_filename': filename_map,
             'include_paths': self.include_paths + APPS_INCLUDE_DIRS,
             'custom_functions': get_custom_functions(),
@@ -131,10 +151,15 @@ def is_latest(self, sourcemap_filename, base):
         sourcemap_file = find_file(sourcemap_filename)
         if not sourcemap_file or not os.path.isfile(sourcemap_file):
             return False
+
         sourcemap_mtime = os.stat(sourcemap_file).st_mtime
+        
         with open(sourcemap_file, 'r') as fp:
             sourcemap = json.load(fp)
         for srcfilename in sourcemap.get('sources'):
+            # 2 fake custom_function in list  for master source scss
+            srcfilename = srcfilename.replace('__presass', '')
+
             srcfilename = os.path.join(base, srcfilename)
             if not os.path.isfile(srcfilename) or os.stat(srcfilename).st_mtime > sourcemap_mtime:
                 # at least one of the source is younger that the sourcemap referring it