diff --git a/Source/WebDriver/ChangeLog b/Source/WebDriver/ChangeLog
index 2f7dc03daa48..84e8446ae8b3 100644
--- a/Source/WebDriver/ChangeLog
+++ b/Source/WebDriver/ChangeLog
@@ -1,3 +1,23 @@
+2017-09-09  Carlos Garcia Campos  <cgarcia@igalia.com>
+
+        WebDriver: ensure we close all windows handles when closing the session
+        https://bugs.webkit.org/show_bug.cgi?id=176508
+
+        Reviewed by Brian Burg.
+
+        The spec says that when closing the session all top level browsing contexts should be closed. We are currently
+        checking if we have an active top level browsing context and then we try to close it before trying with the
+        rest. It can happen that we are in an inconsistent state, for example if the current top level browsing context
+        has been closed by JavaScript or another action and the user didn't switch to another one before closing the
+        session. In such case, closing the session will fail with NoSuchwindow and any other window open will not be
+        closed. It's safer to always ask for all window handles and close them, which is what the spec says too.
+
+        * Session.cpp:
+        (WebDriver::firstWindowHandleInResult): Helper class to get the first window handle in the result array.
+        (WebDriver::Session::closeAllToplevelBrowsingContexts): Use firstWindowHandleInResult().
+        (WebDriver::Session::close): Close the current top level browsing context and get all window handles to close
+        them all if needed.
+
 2017-08-28  Carlos Garcia Campos  <cgarcia@igalia.com>
 
         WebDriver: implement screen capture commands
diff --git a/Source/WebDriver/Session.cpp b/Source/WebDriver/Session.cpp
index 18b69a8347a2..5eceb9c5c415 100644
--- a/Source/WebDriver/Session.cpp
+++ b/Source/WebDriver/Session.cpp
@@ -57,6 +57,18 @@ const Capabilities& Session::capabilities() const
     return m_host->capabilities();
 }
 
+static std::optional<String> firstWindowHandleInResult(InspectorValue& result)
+{
+    RefPtr<InspectorArray> handles;
+    if (result.asArray(handles) && handles->length()) {
+        auto handleValue = handles->get(0);
+        String handle;
+        if (handleValue->asString(handle))
+            return handle;
+    }
+    return std::nullopt;
+}
+
 void Session::closeAllToplevelBrowsingContexts(const String& toplevelBrowsingContext, Function<void (CommandResult&&)>&& completionHandler)
 {
     closeTopLevelBrowsingContext(toplevelBrowsingContext, [this, protectedThis = makeRef(*this), completionHandler = WTFMove(completionHandler)](CommandResult&& result) mutable {
@@ -64,14 +76,9 @@ void Session::closeAllToplevelBrowsingContexts(const String& toplevelBrowsingCon
             completionHandler(WTFMove(result));
             return;
         }
-        RefPtr<InspectorArray> handles;
-        if (result.result()->asArray(handles) && handles->length()) {
-            auto handleValue = handles->get(0);
-            String handle;
-            if (handleValue->asString(handle)) {
-                closeAllToplevelBrowsingContexts(handle, WTFMove(completionHandler));
-                return;
-            }
+        if (auto handle = firstWindowHandleInResult(*result.result())) {
+            closeAllToplevelBrowsingContexts(handle.value(), WTFMove(completionHandler));
+            return;
         }
         completionHandler(CommandResult::success());
     });
@@ -79,13 +86,18 @@ void Session::closeAllToplevelBrowsingContexts(const String& toplevelBrowsingCon
 
 void Session::close(Function<void (CommandResult&&)>&& completionHandler)
 {
-    if (!m_toplevelBrowsingContext) {
+    m_toplevelBrowsingContext = std::nullopt;
+    getWindowHandles([this, completionHandler = WTFMove(completionHandler)](CommandResult&& result) mutable {
+        if (result.isError()) {
+            completionHandler(WTFMove(result));
+            return;
+        }
+        if (auto handle = firstWindowHandleInResult(*result.result())) {
+            closeAllToplevelBrowsingContexts(handle.value(), WTFMove(completionHandler));
+            return;
+        }
         completionHandler(CommandResult::success());
-        return;
-    }
-
-    auto toplevelBrowsingContext = std::exchange(m_toplevelBrowsingContext, std::nullopt);
-    closeAllToplevelBrowsingContexts(toplevelBrowsingContext.value(), WTFMove(completionHandler));
+    });
 }
 
 void Session::setTimeouts(const Timeouts& timeouts, Function<void (CommandResult&&)>&& completionHandler)