diff --git a/external/webL10n/l10n.js b/external/webL10n/l10n.js
index 8b99667a1..3d6bf3107 100644
--- a/external/webL10n/l10n.js
+++ b/external/webL10n/l10n.js
@@ -27,6 +27,7 @@
     - Removes window._ assignment.
     - Remove compatibility code for OldIE.
     - Replaces `String.prototype.substr()` with `String.prototype.substring()`.
+    - Replaces one `Node.insertBefore()` with `Element.prepend()`.
     - Removes `fireL10nReadyEvent` since the "localized" event it dispatches
       is unused and may clash with an identically named event in the viewer.
 */
@@ -921,7 +922,7 @@ document.webL10n = (function(window, document, undefined) {
         // first element child.
         if (!found) {
           var textNode = document.createTextNode(data[gTextProp]);
-          element.insertBefore(textNode, element.firstChild);
+          element.prepend(textNode);
         }
       }
       delete data[gTextProp];
diff --git a/src/display/annotation_layer.js b/src/display/annotation_layer.js
index a6f3eb23a..8d863a1d0 100644
--- a/src/display/annotation_layer.js
+++ b/src/display/annotation_layer.js
@@ -1499,7 +1499,7 @@ class ChoiceWidgetAnnotationElement extends WidgetAnnotationElement {
       noneOptionElement.value = " ";
       noneOptionElement.setAttribute("hidden", true);
       noneOptionElement.setAttribute("selected", true);
-      selectElement.insertBefore(noneOptionElement, selectElement.firstChild);
+      selectElement.prepend(noneOptionElement);
 
       removeEmptyEntry = () => {
         noneOptionElement.remove();
@@ -1573,13 +1573,16 @@ class ChoiceWidgetAnnotationElement extends WidgetAnnotationElement {
           },
           insert(event) {
             const { index, displayValue, exportValue } = event.detail.insert;
+            const selectChild = selectElement.children[index];
             const optionElement = document.createElement("option");
             optionElement.textContent = displayValue;
             optionElement.value = exportValue;
-            selectElement.insertBefore(
-              optionElement,
-              selectElement.children[index]
-            );
+
+            if (selectChild) {
+              selectChild.before(optionElement);
+            } else {
+              selectElement.append(optionElement);
+            }
             storage.setValue(id, {
               value: getValue(event, /* isExport */ true),
               items: getItems(event),
diff --git a/web/base_tree_viewer.js b/web/base_tree_viewer.js
index 4fc37a5fd..c695e6a4e 100644
--- a/web/base_tree_viewer.js
+++ b/web/base_tree_viewer.js
@@ -87,7 +87,7 @@ class BaseTreeViewer {
         this._toggleTreeItem(div, shouldShowAll);
       }
     };
-    div.insertBefore(toggler, div.firstChild);
+    div.prepend(toggler);
   }
 
   /**
diff --git a/web/overlay_manager.js b/web/overlay_manager.js
index cebc1953a..885066106 100644
--- a/web/overlay_manager.js
+++ b/web/overlay_manager.js
@@ -51,7 +51,7 @@ class OverlayManager {
         const style = document.createElement("style");
         style.textContent = PDFJSDev.eval("DIALOG_POLYFILL_CSS");
 
-        document.head.insertBefore(style, document.head.firstElementChild);
+        document.head.prepend(style);
       }
     }
 
diff --git a/web/text_highlighter.js b/web/text_highlighter.js
index fbd238b3d..65c3c1217 100644
--- a/web/text_highlighter.js
+++ b/web/text_highlighter.js
@@ -176,7 +176,7 @@ class TextHighlighter {
       let div = textDivs[divIdx];
       if (div.nodeType === Node.TEXT_NODE) {
         const span = document.createElement("span");
-        div.parentNode.insertBefore(span, div);
+        div.before(span);
         span.append(div);
         textDivs[divIdx] = span;
         div = span;