diff --git a/plugins/platforms/x11/windowed/x11windowed_backend.cpp b/plugins/platforms/x11/windowed/x11windowed_backend.cpp
--- a/plugins/platforms/x11/windowed/x11windowed_backend.cpp
+++ b/plugins/platforms/x11/windowed/x11windowed_backend.cpp
@@ -371,6 +371,7 @@
     if (s != (*it).size) {
         (*it).size = s;
         int x = (*it).internalPosition.x() + s.width();
+        it++;
         for (; it != m_windows.end(); ++it) {
             (*it).internalPosition.setX(x);
             x += (*it).size.width();