diff --git a/testing/web-platform/tests/webdriver/conftest.py b/testing/web-platform/tests/webdriver/conftest.py
index d614cd1be48a..13092678918c 100644
--- a/testing/web-platform/tests/webdriver/conftest.py
+++ b/testing/web-platform/tests/webdriver/conftest.py
@@ -36,6 +36,7 @@ def session(_session, request):
     request.addfinalizer(lambda: cleanup.switch_to_top_level_browsing_context(_session))
     request.addfinalizer(lambda: cleanup.restore_windows(_session))
     request.addfinalizer(lambda: cleanup.dismiss_user_prompts(_session))
+    request.addfinalizer(lambda: cleanup.ensure_valid_window(_session))
 
     return _session
 
diff --git a/testing/web-platform/tests/webdriver/util/cleanup.py b/testing/web-platform/tests/webdriver/util/cleanup.py
index c86d172550fa..7f3232f54816 100644
--- a/testing/web-platform/tests/webdriver/util/cleanup.py
+++ b/testing/web-platform/tests/webdriver/util/cleanup.py
@@ -1,5 +1,14 @@
 import webdriver
 
+
+def ensure_valid_window(session):
+    """If current window is not open anymore, ensure to have a valid one selected."""
+    try:
+        session.window_handle
+    except webdriver.NoSuchWindowException:
+        session.window_handle = session.handles[0]
+
+
 def dismiss_user_prompts(session):
     """Dismisses any open user prompts in windows."""
     current_window = session.window_handle
@@ -13,6 +22,7 @@ def dismiss_user_prompts(session):
 
     session.window_handle = current_window
 
+
 def restore_windows(session):
     """Closes superfluous windows opened by the test without ending
     the session implicitly by closing the last window.
@@ -26,6 +36,7 @@ def restore_windows(session):
 
     session.window_handle = current_window
 
+
 def switch_to_top_level_browsing_context(session):
     """If the current browsing context selected by WebDriver is a
     `<frame>` or an `<iframe>`, switch it back to the top-level
@@ -33,6 +44,7 @@ def switch_to_top_level_browsing_context(session):
     """
     session.switch_frame(None)
 
+
 def _windows(session, exclude=None):
     """Set of window handles, filtered by an `exclude` list if
     provided.