diff --git a/atom/browser/api/atom_api_web_contents.cc b/atom/browser/api/atom_api_web_contents.cc
index 0fab6128332c..94e03b19b968 100644
--- a/atom/browser/api/atom_api_web_contents.cc
+++ b/atom/browser/api/atom_api_web_contents.cc
@@ -1854,7 +1854,7 @@ void WebContents::SetZoomLevel(double level) {
   zoom_controller_->SetZoomLevel(level);
 }
 
-double WebContents::GetZoomLevel() {
+double WebContents::GetZoomLevel() const {
   return zoom_controller_->GetZoomLevel();
 }
 
@@ -1863,7 +1863,7 @@ void WebContents::SetZoomFactor(double factor) {
   SetZoomLevel(level);
 }
 
-double WebContents::GetZoomFactor() {
+double WebContents::GetZoomFactor() const {
   auto level = GetZoomLevel();
   return content::ZoomLevelToZoomFactor(level);
 }
@@ -1884,22 +1884,23 @@ void WebContents::OnGetZoomLevel(content::RenderFrameHost* rfh,
   rfh->Send(reply_msg);
 }
 
-v8::Local<v8::Value> WebContents::GetWebPreferences(v8::Isolate* isolate) {
+v8::Local<v8::Value> WebContents::GetWebPreferences(
+    v8::Isolate* isolate) const {
   auto* web_preferences = WebContentsPreferences::From(web_contents());
   if (!web_preferences)
     return v8::Null(isolate);
   return mate::ConvertToV8(isolate, *web_preferences->preference());
 }
 
-v8::Local<v8::Value> WebContents::GetLastWebPreferences(v8::Isolate* isolate) {
-  WebContentsPreferences* web_preferences =
-      WebContentsPreferences::FromWebContents(web_contents());
+v8::Local<v8::Value> WebContents::GetLastWebPreferences(
+    v8::Isolate* isolate) const {
+  auto* web_preferences = WebContentsPreferences::From(web_contents());
   if (!web_preferences)
     return v8::Null(isolate);
   return mate::ConvertToV8(isolate, *web_preferences->last_preference());
 }
 
-v8::Local<v8::Value> WebContents::GetOwnerBrowserWindow() {
+v8::Local<v8::Value> WebContents::GetOwnerBrowserWindow() const {
   if (owner_window())
     return BrowserWindow::From(isolate(), owner_window());
   else
diff --git a/atom/browser/api/atom_api_web_contents.h b/atom/browser/api/atom_api_web_contents.h
index b6d939307ea3..bb90a9ee498c 100644
--- a/atom/browser/api/atom_api_web_contents.h
+++ b/atom/browser/api/atom_api_web_contents.h
@@ -213,9 +213,9 @@ class WebContents : public mate::TrackableObject<WebContents>,
 
   // Methods for zoom handling.
   void SetZoomLevel(double level);
-  double GetZoomLevel();
+  double GetZoomLevel() const;
   void SetZoomFactor(double factor);
-  double GetZoomFactor();
+  double GetZoomFactor() const;
 
   // Callback triggered on permission response.
   void OnEnterFullscreenModeForTab(content::WebContents* source,
@@ -231,11 +231,11 @@ class WebContents : public mate::TrackableObject<WebContents>,
                       const scoped_refptr<network::ResourceRequestBody>& body);
 
   // Returns the web preferences of current WebContents.
-  v8::Local<v8::Value> GetWebPreferences(v8::Isolate* isolate);
-  v8::Local<v8::Value> GetLastWebPreferences(v8::Isolate* isolate);
+  v8::Local<v8::Value> GetWebPreferences(v8::Isolate* isolate) const;
+  v8::Local<v8::Value> GetLastWebPreferences(v8::Isolate* isolate) const;
 
   // Returns the owner window.
-  v8::Local<v8::Value> GetOwnerBrowserWindow();
+  v8::Local<v8::Value> GetOwnerBrowserWindow() const;
 
   // Grants the child process the capability to access URLs with the origin of
   // the specified URL.
diff --git a/atom/common/options_switches.cc b/atom/common/options_switches.cc
index fd5ae7c83d6e..17a8800d24f5 100644
--- a/atom/common/options_switches.cc
+++ b/atom/common/options_switches.cc
@@ -191,7 +191,6 @@ const char kAppPath[] = "app-path";
 // The command line switch versions of the options.
 const char kBackgroundColor[] = "background-color";
 const char kPreloadScript[] = "preload";
-const char kPreloadURL[] = "preload-url";
 const char kPreloadScripts[] = "preload-scripts";
 const char kNodeIntegration[] = "node-integration";
 const char kContextIsolation[] = "context-isolation";
diff --git a/atom/common/options_switches.h b/atom/common/options_switches.h
index 988defce9f5a..387b11d8d657 100644
--- a/atom/common/options_switches.h
+++ b/atom/common/options_switches.h
@@ -95,7 +95,6 @@ extern const char kAppPath[];
 
 extern const char kBackgroundColor[];
 extern const char kPreloadScript[];
-extern const char kPreloadURL[];
 extern const char kPreloadScripts[];
 extern const char kNodeIntegration[];
 extern const char kContextIsolation[];
diff --git a/lib/browser/guest-window-manager.js b/lib/browser/guest-window-manager.js
index 8e2aa3bb9882..a6effeea8877 100644
--- a/lib/browser/guest-window-manager.js
+++ b/lib/browser/guest-window-manager.js
@@ -63,8 +63,9 @@ const mergeBrowserWindowOptions = function (embedder, options) {
   }
 
   // Inherit certain option values from parent window
+  const webPreferences = embedder.getLastWebPreferences()
   for (const [name, value] of inheritedWebPreferences) {
-    if (embedder.getLastWebPreferences()[name] === value) {
+    if (webPreferences[name] === value) {
       options.webPreferences[name] = value
     }
   }