diff --git a/atom/browser/api/atom_api_browser_window.cc b/atom/browser/api/atom_api_browser_window.cc
index def0640862..04b3e4f1c3 100644
--- a/atom/browser/api/atom_api_browser_window.cc
+++ b/atom/browser/api/atom_api_browser_window.cc
@@ -307,6 +307,10 @@ void BrowserWindow::WillCloseWindow(bool* prevent_default) {
   *prevent_default = Emit("close");
 }
 
+void BrowserWindow::RequestPreferredWidth(int* width) {
+  *width = web_contents()->GetPreferredSize().width();
+}
+
 void BrowserWindow::OnCloseButtonClicked(bool* prevent_default) {
   // When user tries to close the window by clicking the close button, we do
   // not close the window immediately, instead we try to close the web page
diff --git a/atom/browser/api/atom_api_browser_window.h b/atom/browser/api/atom_api_browser_window.h
index 768d975e46..8d0a31b6ee 100644
--- a/atom/browser/api/atom_api_browser_window.h
+++ b/atom/browser/api/atom_api_browser_window.h
@@ -81,6 +81,7 @@ class BrowserWindow : public mate::TrackableObject<BrowserWindow>,
 
   // NativeWindowObserver:
   void WillCloseWindow(bool* prevent_default) override;
+  void RequestPreferredWidth(int* width) override;
   void OnCloseButtonClicked(bool* prevent_default) override;
   void OnWindowClosed() override;
   void OnWindowEndSession() override;
diff --git a/atom/browser/native_window.cc b/atom/browser/native_window.cc
index 1222151248..0dbb3eb0ed 100644
--- a/atom/browser/native_window.cc
+++ b/atom/browser/native_window.cc
@@ -402,6 +402,11 @@ void NativeWindow::PreviewFile(const std::string& path,
 void NativeWindow::CloseFilePreview() {
 }
 
+void NativeWindow::NotifyWindowRequestPreferredWith(int* width) {
+  for (NativeWindowObserver& observer : observers_)
+    observer.RequestPreferredWidth(width);
+}
+
 void NativeWindow::NotifyWindowCloseButtonClicked() {
   // First ask the observers whether we want to close.
   bool prevent_default = false;
diff --git a/atom/browser/native_window.h b/atom/browser/native_window.h
index 7f12f5a23b..3badaf641b 100644
--- a/atom/browser/native_window.h
+++ b/atom/browser/native_window.h
@@ -243,6 +243,7 @@ class NativeWindow : public base::SupportsUserData,
 
   // Public API used by platform-dependent delegates and observers to send UI
   // related notifications.
+  void NotifyWindowRequestPreferredWith(int* width);
   void NotifyWindowCloseButtonClicked();
   void NotifyWindowClosed();
   void NotifyWindowEndSession();
diff --git a/atom/browser/native_window_mac.mm b/atom/browser/native_window_mac.mm
index f4ceaafd12..b71b3f23d5 100644
--- a/atom/browser/native_window_mac.mm
+++ b/atom/browser/native_window_mac.mm
@@ -218,16 +218,16 @@ bool ScopedDisableResize::disable_resize_ = false;
   if ([[NSApp currentEvent] modifierFlags] & NSShiftKeyMask)
     return frame;
 
-  content::WebContents* web_contents = shell_->web_contents();
-  if (!web_contents)
+  // Get preferred width from observers. Usually the page width.
+  int preferred_width = 0;
+  shell_->NotifyWindowRequestPreferredWith(&preferred_width);
+  if (preferred_width <= 0)
     return frame;
 
-  CGFloat page_width = static_cast<CGFloat>(
-      web_contents->GetPreferredSize().width());
-  NSRect window_frame = [window frame];
-
   // Never shrink from the current size on zoom.
-  CGFloat zoomed_width = std::max(page_width, NSWidth(window_frame));
+  NSRect window_frame = [window frame];
+  CGFloat zoomed_width = std::max(static_cast<CGFloat>(preferred_width),
+                                  NSWidth(window_frame));
 
   // |frame| determines our maximum extents. We need to set the origin of the
   // frame -- and only move it left if necessary.
diff --git a/atom/browser/native_window_observer.h b/atom/browser/native_window_observer.h
index 27f5cb92f8..4dfd352109 100644
--- a/atom/browser/native_window_observer.h
+++ b/atom/browser/native_window_observer.h
@@ -34,6 +34,9 @@ class NativeWindowObserver {
   // Called when the window is gonna closed.
   virtual void WillCloseWindow(bool* prevent_default) {}
 
+  // Called when the window wants to know the preferred width.
+  virtual void RequestPreferredWidth(int* width) {}
+
   // Called when closed button is clicked.
   virtual void OnCloseButtonClicked(bool* prevent_default) {}