diff --git a/toolkit/components/browser/nsWebBrowser.cpp b/toolkit/components/browser/nsWebBrowser.cpp
index b119a17bbe05..c33803b50afb 100644
--- a/toolkit/components/browser/nsWebBrowser.cpp
+++ b/toolkit/components/browser/nsWebBrowser.cpp
@@ -170,8 +170,7 @@ already_AddRefed<nsWebBrowser> nsWebBrowser::Create(
   return browser.forget();
 }
 
-NS_IMETHODIMP
-nsWebBrowser::InternalDestroy() {
+void nsWebBrowser::InternalDestroy() {
   if (mInternalWidget) {
     mInternalWidget->SetWidgetListener(nullptr);
     mInternalWidget->Destroy();
@@ -184,8 +183,6 @@ nsWebBrowser::InternalDestroy() {
     mDocShellTreeOwner->WebBrowser(nullptr);
     mDocShellTreeOwner = nullptr;
   }
-
-  return NS_OK;
 }
 
 NS_IMPL_CYCLE_COLLECTING_ADDREF(nsWebBrowser)
diff --git a/toolkit/components/browser/nsWebBrowser.h b/toolkit/components/browser/nsWebBrowser.h
index 189749461ba3..60dd4fadfe6a 100644
--- a/toolkit/components/browser/nsWebBrowser.h
+++ b/toolkit/components/browser/nsWebBrowser.h
@@ -113,7 +113,7 @@ class nsWebBrowser final : public nsIWebBrowser,
 
  protected:
   virtual ~nsWebBrowser();
-  NS_IMETHOD InternalDestroy();
+  void InternalDestroy();
 
   // XXXbz why are these NS_IMETHOD?  They're not interface methods!
   NS_IMETHOD SetDocShell(nsIDocShell* aDocShell);