diff --git a/web/event_utils.js b/web/event_utils.js
index 3ae6910be..e1d327288 100644
--- a/web/event_utils.js
+++ b/web/event_utils.js
@@ -172,7 +172,7 @@ class AutomationEventBus extends EventBus {
     }
     super.dispatch(eventName, data);
 
-    const details = Object.create(null);
+    const detail = Object.create(null);
     if (data) {
       for (const key in data) {
         const value = data[key];
@@ -182,11 +182,14 @@ class AutomationEventBus extends EventBus {
           }
           continue; // Ignore the `source` property.
         }
-        details[key] = value;
+        detail[key] = value;
       }
     }
-    const event = document.createEvent("CustomEvent");
-    event.initCustomEvent(eventName, true, true, details);
+    const event = new CustomEvent(eventName, {
+      bubbles: true,
+      cancelable: true,
+      detail,
+    });
     document.dispatchEvent(event);
   }
 }
diff --git a/web/firefoxcom.js b/web/firefoxcom.js
index 141024f3b..137af0c3f 100644
--- a/web/firefoxcom.js
+++ b/web/firefoxcom.js
@@ -40,11 +40,14 @@ class FirefoxCom {
     const request = document.createTextNode("");
     document.documentElement.append(request);
 
-    const sender = document.createEvent("CustomEvent");
-    sender.initCustomEvent("pdf.js.message", true, false, {
-      action,
-      data,
-      sync: true,
+    const sender = new CustomEvent("pdf.js.message", {
+      bubbles: true,
+      cancelable: false,
+      detail: {
+        action,
+        data,
+        sync: true,
+      },
     });
     request.dispatchEvent(sender);
     const response = sender.detail.response;
@@ -88,12 +91,15 @@ class FirefoxCom {
     }
     document.documentElement.append(request);
 
-    const sender = document.createEvent("CustomEvent");
-    sender.initCustomEvent("pdf.js.message", true, false, {
-      action,
-      data,
-      sync: false,
-      responseExpected: !!callback,
+    const sender = new CustomEvent("pdf.js.message", {
+      bubbles: true,
+      cancelable: false,
+      detail: {
+        action,
+        data,
+        sync: false,
+        responseExpected: !!callback,
+      },
     });
     request.dispatchEvent(sender);
   }
diff --git a/web/pdf_print_service.js b/web/pdf_print_service.js
index 4b522a80e..52af95969 100644
--- a/web/pdf_print_service.js
+++ b/web/pdf_print_service.js
@@ -273,8 +273,11 @@ window.print = function () {
 };
 
 function dispatchEvent(eventType) {
-  const event = document.createEvent("CustomEvent");
-  event.initCustomEvent(eventType, false, false, "custom");
+  const event = new CustomEvent(eventType, {
+    bubbles: false,
+    cancelable: false,
+    detail: "custom",
+  });
   window.dispatchEvent(event);
 }