diff --git a/lib/damask/config/material.py b/lib/damask/config/material.py
index d59aaa6a9..a56c5d976 100644
--- a/lib/damask/config/material.py
+++ b/lib/damask/config/material.py
@@ -101,8 +101,6 @@ class Texture(Section):
 class Material():
   """Reads, manipulates and writes material.config files"""
 
-  __slots__ = ['data']
-
   def __init__(self,verbose=True):
     """Generates ordered list of parts"""
     self.parts = [