diff --git a/src/rougail/annotator/fill.py b/src/rougail/annotator/fill.py
index 481979de3..6d002767c 100644
--- a/src/rougail/annotator/fill.py
+++ b/src/rougail/annotator/fill.py
@@ -47,6 +47,7 @@ class FillAnnotator(TargetAnnotator, ParamAnnotator):
                 not hasattr(self.objectspace.space.constraints, 'fill'):
             return
         self.functions = dir(load_modules(eosfunc_file))
+        self.functions.extend(self.objectspace.rougailconfig['internal_functions'])
         self.target_is_uniq = True
         self.only_variable = True
         self.allow_function = False