--- a/devtools/client/accessibility/accessibility-startup.js
+++ b/devtools/client/accessibility/accessibility-startup.js
@@ -37,16 +37,21 @@ class AccessibilityStartup {
    * Fully initialize accessibility front. Also add listeners for accessibility
    * service lifecycle events that affect the state of the tool tab highlight.
    * @return {Promise}
    *         A promise for when accessibility front is fully initialized.
    */
   initAccessibility() {
     if (!this._initAccessibility) {
       this._initAccessibility = (async function() {
+        await Promise.race([
+          this.toolbox.isOpen,
+          this.toolbox.once("accessibility-init"),
+        ]);
+
         this._accessibility = this.target.getFront("accessibility");
         // We must call a method on an accessibility front here (such as getWalker), in
         // oreder to be able to check actor's backward compatibility via actorHasMethod.
         // See targe.js@getActorDescription for more information.
         this._walker = await this._accessibility.getWalker();
         this._supports = {};
         // Only works with FF61+ targets
         this._supports.enableDisable =