diff --git a/PyMca5/PyMcaPhysics/xrf/ClassMcaTheory.py b/PyMca5/PyMcaPhysics/xrf/ClassMcaTheory.py
index 9fb975424..6ef4d59f9 100644
--- a/PyMca5/PyMcaPhysics/xrf/ClassMcaTheory.py
+++ b/PyMca5/PyMcaPhysics/xrf/ClassMcaTheory.py
@@ -227,6 +227,8 @@ def __configure(self):
             energyscatter = []
 
             for i in range(len(self.config['fit']['energy'])):
+                if self.config['fit']['energy'][i] == "None":
+                    self.config['fit']['energy'][i] = None
                 if self.config['fit']['energyflag'][i]:
                     if self.config['fit']['energy'][i] is not None:
                         energyflag.append(self.config['fit']['energyflag'][i])