diff --git a/shell_client.h b/shell_client.h
--- a/shell_client.h
+++ b/shell_client.h
@@ -61,6 +61,9 @@
     KWayland::Server::ShellSurfaceInterface *shellSurface() const {
         return m_shellSurface;
     }
+    KWayland::Server::XdgShellSurfaceInterface *xdgShellSurface() const {
+        return m_xdgShellSurface;
+    }
 
     void blockActivityUpdates(bool b = true) override;
     QString caption(bool full = true) const override;
diff --git a/shell_client.cpp b/shell_client.cpp
--- a/shell_client.cpp
+++ b/shell_client.cpp
@@ -253,6 +253,12 @@
     getShadow();
     connect(s, &SurfaceInterface::shadowChanged, this, &Toplevel::getShadow);
 
+    connect(waylandServer(), &WaylandServer::foreignTransientChanged, this, [this](KWayland::Server::SurfaceInterface *child, KWayland::Server::SurfaceInterface *parent) {
+        Q_UNUSED(parent)
+        if (child == surface()) {
+            setTransient();
+        }
+    });
     setTransient();
     // check whether we have a ServerSideDecoration
     if (ServerSideDecorationInterface *deco = ServerSideDecorationInterface::get(s)) {
@@ -1320,6 +1326,9 @@
     if (m_xdgShellPopup) {
         s = m_xdgShellPopup->transientFor().data();
     }
+    if (!s) {
+        s = waylandServer()->findForeignTransientForSurface(surface());
+    }
     auto t = waylandServer()->findClient(s);
     if (t != transientFor()) {
         // remove from main client
diff --git a/wayland_server.h b/wayland_server.h
--- a/wayland_server.h
+++ b/wayland_server.h
@@ -56,6 +56,7 @@
 class OutputManagementInterface;
 class OutputConfigurationInterface;
 class XdgShellInterface;
+class XdgForeignInterface;
 }
 }
 
@@ -113,6 +114,11 @@
     ShellClient *findClient(QWindow *w) const;
 
     /**
+     * return a transient parent of a surface imported with the foreign protocol, if any
+     */
+    KWayland::Server::SurfaceInterface *findForeignTransientForSurface(KWayland::Server::SurfaceInterface *surface);
+
+    /**
      * @returns file descriptor for Xwayland to connect to.
      **/
     int createXWaylandConnection();
@@ -189,6 +195,7 @@
     void shellClientRemoved(KWin::ShellClient*);
     void terminatingInternalClientConnection();
     void initialized();
+    void foreignTransientChanged(KWayland::Server::SurfaceInterface *child, KWayland::Server::SurfaceInterface *parent);
 
 private:
     void setupX11ClipboardSync();
@@ -229,6 +236,7 @@
         KWayland::Server::ClientConnection *client = nullptr;
         QPointer<KWayland::Server::DataDeviceInterface> ddi;
     } m_xclipbaordSync;
+    KWayland::Server::XdgForeignInterface *m_XdgForeign = nullptr;
     QList<ShellClient*> m_clients;
     QList<ShellClient*> m_internalClients;
     QHash<KWayland::Server::ClientConnection*, quint16> m_clientIds;
diff --git a/wayland_server.cpp b/wayland_server.cpp
--- a/wayland_server.cpp
+++ b/wayland_server.cpp
@@ -52,6 +52,7 @@
 #include <KWayland/Server/outputmanagement_interface.h>
 #include <KWayland/Server/outputconfiguration_interface.h>
 #include <KWayland/Server/xdgshell_interface.h>
+#include <KWayland/Server/xdgforeign_interface.h>
 
 // Qt
 #include <QThread>
@@ -158,6 +159,20 @@
     } else {
         connect(client, &ShellClient::windowShown, this, &WaylandServer::shellClientShown);
     }
+    //client->installXdgForeignInterface(m_XdgForeign);
+    connect(m_XdgForeign, &KWayland::Server::XdgForeignInterface::transientChanged, client, [this, client](KWayland::Server::SurfaceInterface *child, KWayland::Server::SurfaceInterface *parent) {
+        ShellClient *childClient = findClient(child);
+        //we are the parent, child is changed, manage all in this branch
+        if (findClient(parent) == client) {
+            if (childClient && client && client->surface() == parent) {
+                childClient->setModal(true);
+            }
+        //we are the child, just manage parent lost in this case
+        } else if (childClient == client && !parent) {
+            childClient->setModal(false);
+        }
+        emit foreignTransientChanged(child, parent);
+    });
 }
 
 bool WaylandServer::init(const QByteArray &socketName, InitalizationFlags flags)
@@ -301,9 +316,17 @@
 
     m_display->createSubCompositor(m_display)->create();
 
+    m_XdgForeign = m_display->createXdgForeignUnstableInterface(m_display);
+    m_XdgForeign->create();
+
     return true;
 }
 
+SurfaceInterface *WaylandServer::findForeignTransientForSurface(SurfaceInterface *surface)
+{
+    return m_XdgForeign->transientFor(surface);
+}
+
 void WaylandServer::shellClientShown(Toplevel *t)
 {
     ShellClient *c = dynamic_cast<ShellClient*>(t);