diff --git a/docshell/base/nsDocShell.cpp b/docshell/base/nsDocShell.cpp
index ad92fa14fff8..f19328ef65bb 100644
--- a/docshell/base/nsDocShell.cpp
+++ b/docshell/base/nsDocShell.cpp
@@ -2708,25 +2708,6 @@ nsDocShell::GetInProcessSameTypeParent(nsIDocShellTreeItem** aParent) {
   return NS_OK;
 }
 
-NS_IMETHODIMP
-nsDocShell::GetSameTypeInProcessParentIgnoreBrowserBoundaries(
-    nsIDocShell** aParent) {
-  NS_ENSURE_ARG_POINTER(aParent);
-  *aParent = nullptr;
-
-  nsCOMPtr<nsIDocShellTreeItem> parent =
-      do_QueryInterface(GetAsSupports(mParent));
-  if (!parent) {
-    return NS_OK;
-  }
-
-  if (parent->ItemType() == mItemType) {
-    nsCOMPtr<nsIDocShell> parentDS = do_QueryInterface(parent);
-    parentDS.forget(aParent);
-  }
-  return NS_OK;
-}
-
 NS_IMETHODIMP
 nsDocShell::GetInProcessRootTreeItem(nsIDocShellTreeItem** aRootTreeItem) {
   NS_ENSURE_ARG_POINTER(aRootTreeItem);
diff --git a/docshell/base/nsIDocShell.idl b/docshell/base/nsIDocShell.idl
index d2316b46682b..0b7fac567219 100644
--- a/docshell/base/nsIDocShell.idl
+++ b/docshell/base/nsIDocShell.idl
@@ -539,14 +539,6 @@ interface nsIDocShell : nsIDocShellTreeItem
    */
   [infallible] readonly attribute boolean isTopLevelContentDocShell;
 
-  /**
-   * Like nsIDocShellTreeItem::GetSameTypeParent, except this ignores <iframe
-   * mozbrowser> boundaries. Which no longer exist.
-   *
-   * @deprecated: Use `BrowsingContext::GetParent()` in the future.
-   */
-  nsIDocShell getSameTypeInProcessParentIgnoreBrowserBoundaries();
-
   /**
    * True iff asynchronous panning and zooming is enabled for this
    * docshell.
diff --git a/dom/base/nsGlobalWindowOuter.cpp b/dom/base/nsGlobalWindowOuter.cpp
index 60824f425ebe..938a6f1030b3 100644
--- a/dom/base/nsGlobalWindowOuter.cpp
+++ b/dom/base/nsGlobalWindowOuter.cpp
@@ -3124,26 +3124,17 @@ nsPIDOMWindowOuter* nsGlobalWindowOuter::GetInProcessScriptableParentOrNull() {
   return (nsGlobalWindowOuter::Cast(parent) == this) ? nullptr : parent;
 }
 
-/**
- * nsPIDOMWindow::GetParent (when called from C++) is just a wrapper around
- * GetRealParent.
- */
 already_AddRefed<nsPIDOMWindowOuter> nsGlobalWindowOuter::GetInProcessParent() {
   if (!mDocShell) {
     return nullptr;
   }
 
-  nsCOMPtr<nsIDocShell> parent;
-  mDocShell->GetSameTypeInProcessParentIgnoreBrowserBoundaries(
-      getter_AddRefs(parent));
-
-  if (parent) {
-    nsCOMPtr<nsPIDOMWindowOuter> win = parent->GetWindow();
-    return win.forget();
+  if (auto* parentBC = GetBrowsingContext()->GetParent()) {
+    if (auto* parent = parentBC->GetDOMWindow()) {
+      return do_AddRef(parent);
+    }
   }
-
-  nsCOMPtr<nsPIDOMWindowOuter> win(this);
-  return win.forget();
+  return do_AddRef(this);
 }
 
 static nsresult GetTopImpl(nsGlobalWindowOuter* aWin, nsIURI* aURIBeingLoaded,
diff --git a/tools/lint/eslint/eslint-plugin-mozilla/tests/xpidl/docshell.xpt b/tools/lint/eslint/eslint-plugin-mozilla/tests/xpidl/docshell.xpt
index 502520781302..fc8a45216bf7 100644
--- a/tools/lint/eslint/eslint-plugin-mozilla/tests/xpidl/docshell.xpt
+++ b/tools/lint/eslint/eslint-plugin-mozilla/tests/xpidl/docshell.xpt
@@ -2652,23 +2652,6 @@
           }
         ]
       },
-      {
-        "flags": [
-          "hasretval"
-        ],
-        "name": "getSameTypeInProcessParentIgnoreBrowserBoundaries",
-        "params": [
-          {
-            "flags": [
-              "out"
-            ],
-            "type": {
-              "name": "nsIDocShell",
-              "tag": "TD_INTERFACE_TYPE"
-            }
-          }
-        ]
-      },
       {
         "flags": [
           "getter",