--- a/dom/base/nsDocument.cpp
+++ b/dom/base/nsDocument.cpp
@@ -13605,17 +13605,17 @@ nsIDocument::ClearStaleServoDataFromDocu
     ServoRestyleManager::ClearServoDataFromSubtree(root);
   }
   mMightHaveStaleServoData = false;
 }
 
 Selection*
 nsIDocument::GetSelection(ErrorResult& aRv)
 {
-  nsCOMPtr<nsPIDOMWindowInner> window = do_QueryInterface(GetScopeObject());
+  nsCOMPtr<nsPIDOMWindowInner> window = GetInnerWindow();
   if (!window) {
     return nullptr;
   }
 
   NS_ASSERTION(window->IsInnerWindow(), "Should have inner window here!");
   if (!window->IsCurrentInnerWindow()) {
     return nullptr;
   }

--- a/testing/web-platform/meta/selection/getSelection.html.ini
+++ b/testing/web-platform/meta/selection/getSelection.html.ini
@@ -1,17 +1,8 @@
 [getSelection.html]
   type: testharness
-  [getSelection() on HTML document with null defaultView must be null]
-    expected: FAIL
-
-  [getSelection() on XML document with null defaultView must be null]
-    expected: FAIL
-
-  [getSelection() on HTML document with null defaultView must be null inside an iframe onload]
-    expected: FAIL
-
   [window.getSelection() instanceof Selection in an iframe immediately after appendChild]
     expected: FAIL
 
   [document.getSelection() instanceof Selection in an iframe immediately after appendChild]
     expected: FAIL