diff --git a/xdgshellclient.cpp b/xdgshellclient.cpp
--- a/xdgshellclient.cpp
+++ b/xdgshellclient.cpp
@@ -780,7 +780,7 @@
     // call into decoration update borders
     if (isDecorated() && decoration()->client() && !(options->borderlessMaximizedWindows() && m_requestedMaximizeMode == KWin::MaximizeFull)) {
         changeMaximizeRecursion = true;
-        const auto c = decoration()->client().data();
+        const auto c = decoration()->client().toStrongRef();
         if ((m_requestedMaximizeMode & MaximizeVertical) != (oldMode & MaximizeVertical)) {
             emit c->maximizedVerticallyChanged(m_requestedMaximizeMode & MaximizeVertical);
         }