diff --git a/CHANGELOG.md b/CHANGELOG.md
index 1d090b70..c47c6e05 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,6 +10,7 @@ CHANGELOG for FlatCAM beta
 23.10.2020
 
 - updated Copper Thieving Tool to work with the updated program
+- updated Rules Check Tool - Hole Size rule to work with the new data structure for the Excellon objects
 
 22.10.2020
 
diff --git a/appTools/ToolRulesCheck.py b/appTools/ToolRulesCheck.py
index ff105265..f6bf9e60 100644
--- a/appTools/ToolRulesCheck.py
+++ b/appTools/ToolRulesCheck.py
@@ -357,7 +357,7 @@ class RulesCheck(AppTool):
 
             name = elem['name']
             for tool in elem['tools']:
-                tool_dia = float('%.*f' % (4, float(elem['tools'][tool]['C'])))
+                tool_dia = float('%.*f' % (4, float(elem['tools'][tool]['tooldia'])))
                 if tool_dia < float(size):
                     dia_list.append(tool_dia)
             obj_violations['name'] = name