diff --git a/package.json b/package.json
index 539220bd..db965cc6 100644
--- a/package.json
+++ b/package.json
@@ -53,7 +53,7 @@
     {
       "path": "lib/index.js",
       "import": "{controller, attr, target, targets}",
-      "limit": "1.6kb"
+      "limit": "1.64kb"
     }
   ]
 }
diff --git a/src/register.ts b/src/register.ts
index 94b64ef7..ecc87265 100644
--- a/src/register.ts
+++ b/src/register.ts
@@ -10,10 +10,17 @@ import {dasherize} from './dasherize.js'
  */
 export function register(classObject: CustomElement): void {
   const name = dasherize(classObject.name).replace(/-element$/, '')
-  if (!window.customElements.get(name)) {
+
+  try {
+    window.customElements.define(name, classObject)
     // eslint-disable-next-line @typescript-eslint/ban-ts-comment
     // @ts-ignore
-    window[classObject.name] = classObject
-    window.customElements.define(name, classObject)
+    window[classObject.name] = customElements.get(name)
+  } catch (e: unknown) {
+    // The only reason for window.customElements.define to throw a `NotSupportedError`
+    // is if the element has already been defined.
+    if (e instanceof DOMException && e.name === 'NotSupportedError') return
+
+    throw e
   }
 }