diff --git a/browser/components/urlbar/tests/browser/browser_locationBarExternalLoad.js b/browser/components/urlbar/tests/browser/browser_locationBarExternalLoad.js
index 1b1da7510d7e..3560179be40d 100644
--- a/browser/components/urlbar/tests/browser/browser_locationBarExternalLoad.js
+++ b/browser/components/urlbar/tests/browser/browser_locationBarExternalLoad.js
@@ -76,14 +76,6 @@ async function testURL(url, loadFunc, endFunc) {
         null,
         "focusedElement not null"
       );
-
-      if (arg.isRemote) {
-        Assert.equal(
-          Services.focus.activeWindow,
-          content,
-          "activeWindow not correct"
-        );
-      }
     }
   );
 
diff --git a/dom/base/nsFocusManager.cpp b/dom/base/nsFocusManager.cpp
index 544f0dbd86b2..0af84b89b020 100644
--- a/dom/base/nsFocusManager.cpp
+++ b/dom/base/nsFocusManager.cpp
@@ -359,7 +359,8 @@ InputContextAction::Cause nsFocusManager::GetFocusMoveActionCause(
 
 NS_IMETHODIMP
 nsFocusManager::GetActiveWindow(mozIDOMWindowProxy** aWindow) {
-  // TODO mActiveWindow in content process
+  MOZ_ASSERT(XRE_IsParentProcess(),
+             "Must not be called outside the parent process.");
   NS_IF_ADDREF(*aWindow = mActiveWindow);
   return NS_OK;
 }
diff --git a/dom/base/test/chrome/bug418986-1.js b/dom/base/test/chrome/bug418986-1.js
index 8e8408c9b331..72653a7718c4 100644
--- a/dom/base/test/chrome/bug418986-1.js
+++ b/dom/base/test/chrome/bug418986-1.js
@@ -7,8 +7,10 @@ var test = function(isContent) {
     set: [["security.allow_eval_with_system_principal", true]],
   });
 
-  let { ww } = SpecialPowers.Services;
-  window.chromeWindow = ww.activeWindow;
+  if (!isContent) {
+    let { ww } = SpecialPowers.Services;
+    window.chromeWindow = ww.activeWindow;
+  }
 
   // The pairs of values expected to be the same when
   // fingerprinting resistance is enabled.
@@ -62,11 +64,11 @@ var test = function(isContent) {
         pairs.map(function([item, onVal]) {
           if (resisting) {
             checkPair("window." + item, onVal);
-          } else if (!item.startsWith("moz")) {
+          } else if (!isContent && !item.startsWith("moz")) {
             checkPair("window." + item, "chromeWindow." + item);
           }
         });
-        if (!resisting) {
+        if (!isContent && !resisting) {
           // Hard to predict these values, but we can enforce constraints:
           ok(
             window.mozInnerScreenX >= chromeWindow.mozInnerScreenX,
diff --git a/dom/interfaces/base/nsIFocusManager.idl b/dom/interfaces/base/nsIFocusManager.idl
index 8036fa4e30d8..9da5076fe588 100644
--- a/dom/interfaces/base/nsIFocusManager.idl
+++ b/dom/interfaces/base/nsIFocusManager.idl
@@ -46,7 +46,7 @@ interface nsIFocusManager : nsISupports
 {
   /**
    * The most active (frontmost) window, or null if no window that is part of
-   * the application is active.
+   * the application is active. Do not use outside the parent process.
    */
   readonly attribute mozIDOMWindowProxy activeWindow;