Don't attempt to use attachShadow if the browser doesn't support it

src/withPseudoState.js

@@ -52,13 +52,15 @@ function initPseudoStyles(shadowRoot) {
 // Reinitialize CSS enhancements every time the story changes
 addons.getChannel().on(STORY_RENDERED, () => initPseudoStyles())
 
-// Monkeypatch the attachShadow method so we can handle pseudo styles inside shadow DOM
-Element.prototype._attachShadow = Element.prototype.attachShadow
-Element.prototype.attachShadow = function attachShadow(init) {
-  if (!this._attachShadow) return // IE doesn't support shadow DOM
-  const shadowRoot = this._attachShadow({ ...init, mode: "open" })
-  setTimeout(() => initPseudoStyles(shadowRoot))
-  return shadowRoot
+// IE doesn't support shadow DOM
+if (Element.prototype.attachShadow) {
+  // Monkeypatch the attachShadow method so we can handle pseudo styles inside shadow DOM
+  Element.prototype._attachShadow = Element.prototype.attachShadow
+  Element.prototype.attachShadow = function attachShadow(init) {
+    const shadowRoot = this._attachShadow({ ...init, mode: "open" })
+    setTimeout(() => initPseudoStyles(shadowRoot))
+    return shadowRoot
+  }
 }
 
 export const withPseudoState = (StoryFn) => {

stories/ShadowRoot.js

@@ -4,6 +4,7 @@ export const ShadowRoot = () => {
   const ref = React.useRef()
 
   React.useEffect(() => {
+    if (!ref.current.attachShadow) return
     ref.current.attachShadow({ mode: "closed" })
     ref.current.shadowRoot.innerHTML = `
       <style>