diff --git a/dom/base/nsDOMWindowUtils.cpp b/dom/base/nsDOMWindowUtils.cpp
index b4e2573966e8..e2f247a149c2 100644
--- a/dom/base/nsDOMWindowUtils.cpp
+++ b/dom/base/nsDOMWindowUtils.cpp
@@ -2149,6 +2149,13 @@ nsDOMWindowUtils::IsInModalState(bool* retval) {
   return NS_OK;
 }
 
+NS_IMETHODIMP
+nsDOMWindowUtils::GetDesktopModeViewport(bool* retval) {
+  nsCOMPtr<nsPIDOMWindowOuter> window = do_QueryReferent(mWindow);
+  *retval = window && window->IsDesktopModeViewport();
+  return NS_OK;
+}
+
 NS_IMETHODIMP
 nsDOMWindowUtils::SetDesktopModeViewport(bool aDesktopMode) {
   nsCOMPtr<nsPIDOMWindowOuter> window = do_QueryReferent(mWindow);
diff --git a/dom/interfaces/base/nsIDOMWindowUtils.idl b/dom/interfaces/base/nsIDOMWindowUtils.idl
index 6b3159579b6c..5b4618b32a51 100644
--- a/dom/interfaces/base/nsIDOMWindowUtils.idl
+++ b/dom/interfaces/base/nsIDOMWindowUtils.idl
@@ -1323,9 +1323,9 @@ interface nsIDOMWindowUtils : nsISupports {
   boolean isInModalState();
 
   /**
-   * Request set internal desktopMode flag change.
+   * Internal desktopMode flag.
    */
-  void setDesktopModeViewport(in boolean aDesktopModeViewport);
+  attribute boolean desktopModeViewport;
 
   /**
    * Suspend/resume timeouts on this window and its descendant windows.