--- a/devtools/server/actors/root.js
+++ b/devtools/server/actors/root.js
@@ -226,16 +226,19 @@ RootActor.prototype = {
       this._parameters.addonList.onListChanged = null;
     }
     if (this._parameters.workerList) {
       this._parameters.workerList.onListChanged = null;
     }
     if (this._parameters.serviceWorkerRegistrationList) {
       this._parameters.serviceWorkerRegistrationList.onListChanged = null;
     }
+    if (this._parameters.processList) {
+      this._parameters.processList.onListChanged = null;
+    }
     if (typeof this._parameters.onShutdown === "function") {
       this._parameters.onShutdown();
     }
     this._extraActors = null;
     this.conn = null;
     this._tabActorPool = null;
     this._globalActorPool = null;
     this._windowActorPool = null;