diff --git a/MO4/ruleset.xml b/MO4/ruleset.xml
index 4fcf470..acd4451 100644
--- a/MO4/ruleset.xml
+++ b/MO4/ruleset.xml
@@ -133,6 +133,8 @@
     <rule ref="SlevomatCodingStandard.ControlStructures.RequireNullCoalesceOperator"/>
     <!-- Require usage of null coalesce equal operator when possible -->
     <rule ref="SlevomatCodingStandard.ControlStructures.RequireNullCoalesceEqualOperator"/>
+    <!-- Require usage of null safe operator when possible -->
+    <rule ref="SlevomatCodingStandard.ControlStructures.RequireNullSafeObjectOperator"/>
     <!-- Require usage of ternary operator when possible -->
     <rule ref="SlevomatCodingStandard.ControlStructures.RequireTernaryOperator">
         <!-- But multiline is useful for readability -->