diff --git a/Userland/Libraries/LibWeb/CSS/StyleComputer.cpp b/Userland/Libraries/LibWeb/CSS/StyleComputer.cpp
index 3d7a496d3dc..de570b6c85f 100644
--- a/Userland/Libraries/LibWeb/CSS/StyleComputer.cpp
+++ b/Userland/Libraries/LibWeb/CSS/StyleComputer.cpp
@@ -315,12 +315,12 @@ Vector<MatchingRule> StyleComputer::collect_matching_rules(DOM::Element const& e
         if (pseudo_element.has_value()) {
             for (auto const& rule : rules) {
                 if (rule.contains_pseudo_element && filter_namespace_rule(element, rule))
-                    rules_to_run.append(rule);
+                    rules_to_run.unchecked_append(rule);
             }
         } else {
             for (auto const& rule : rules) {
                 if (filter_namespace_rule(element, rule))
-                    rules_to_run.append(rule);
+                    rules_to_run.unchecked_append(rule);
             }
         }
     };