diff --git a/src/gui/kernel/qwidget_x11.cpp b/src/gui/kernel/qwidget_x11.cpp
index 5ece7d6..ab83d33 100644
--- a/src/gui/kernel/qwidget_x11.cpp
+++ b/src/gui/kernel/qwidget_x11.cpp
@@ -2691,8 +2691,16 @@ void QWidgetPrivate::setConstraints_sys()
 #ifdef ALIEN_DEBUG
     qDebug() << "QWidgetPrivate::setConstraints_sys START" << q;
 #endif
-    if (q->testAttribute(Qt::WA_WState_Created))
+    if (q->testAttribute(Qt::WA_WState_Created)) {
         do_size_hints(q, extra);
+        QtMWMHints mwmHints = GetMWMHints(X11->display, q->internalWinId());
+        if (q->minimumSize() == q->maximumSize()) {
+            mwmHints.functions &= ~MWM_FUNC_RESIZE;
+        } else {
+            mwmHints.functions |= MWM_FUNC_RESIZE;
+        }
+        SetMWMHints(X11->display, q->internalWinId(), mwmHints);
+    }
 #ifdef ALIEN_DEBUG
     qDebug() << "QWidgetPrivate::setConstraints_sys END" << q;
 #endif