diff --git a/dom/base/nsTreeSanitizer.cpp b/dom/base/nsTreeSanitizer.cpp
index 9f2bba1ad6ce..2331818724fc 100644
--- a/dom/base/nsTreeSanitizer.cpp
+++ b/dom/base/nsTreeSanitizer.cpp
@@ -1823,11 +1823,14 @@ bool nsTreeSanitizer::SanitizeInlineStyle(
 }
 
 void nsTreeSanitizer::RemoveConditionalCSSFromSubtree(nsINode* aRoot) {
+  AutoTArray<RefPtr<nsINode>, 10> nodesToSanitize;
   for (nsINode* node : ShadowIncludingTreeIterator(*aRoot)) {
-    if (!node->IsHTMLElement(nsGkAtoms::style) &&
-        !node->IsSVGElement(nsGkAtoms::style)) {
-      continue;
+    if (node->IsHTMLElement(nsGkAtoms::style) ||
+        node->IsSVGElement(nsGkAtoms::style)) {
+      nodesToSanitize.AppendElement(node);
     }
+  }
+  for (nsINode* node : nodesToSanitize) {
     SanitizeInlineStyle(node->AsElement(),
                         StyleSanitizationKind::NoConditionalRules);
   }
diff --git a/parser/xml/test/unit/test_sanitizer_style.js b/parser/xml/test/unit/test_sanitizer_style.js
index 5939e1bdb37d..6f00295cda67 100644
--- a/parser/xml/test/unit/test_sanitizer_style.js
+++ b/parser/xml/test/unit/test_sanitizer_style.js
@@ -71,6 +71,10 @@ const kConditionalCSSTestCases = [
     data: `#foo { display: none } @media (min-width: 300px) { #bar { display: none } }`,
     sanitized: `#foo { display: none }`,
   },
+  {
+    data: `@media (min-width: 300px) { #bar { display: none } }`,
+    sanitized: ``,
+  },
 ];
 
 function run_test() {