diff --git a/src/rdf-mappings/functions.py b/src/rdf-mappings/functions.py
index a65c6bdc9d57d8c3af54696ec1414ebd43e896e9..e9adcdc48a537490aee067f8a0d31f84f0ca9794 100644
--- a/src/rdf-mappings/functions.py
+++ b/src/rdf-mappings/functions.py
@@ -44,7 +44,7 @@ def clean_class_name_string(input_string):
     Cleans string that is to be used as a class name from unwanted characters.
     """
 
-    char_list = ["'", '"', '.', '+', ',', '*', '&', '/', '=', '’', ';', ':' '¨', '#', '?', '\n', '(', ')', '<', '>', '{', '}']
+    char_list = ["'", '"', '.', '+', ',', '*', '&', '/', '=', '’', ';', ':' '¨', '#', '?', '\n', '(', ')', '<', '>', '{', '}', '!']
 
     for char in char_list:
         input_string = input_string.replace(char, '')