diff --git a/src/qwaylandlayersurface.cpp b/src/qwaylandlayersurface.cpp
index 1d12b05..c6beb6f 100644
--- a/src/qwaylandlayersurface.cpp
+++ b/src/qwaylandlayersurface.cpp
@@ -133,6 +133,7 @@ void QWaylandLayerSurface::applyConfigure()
     window()->resizeFromApplyConfigure(m_pendingSize);
 }
 
+#if QT_VERSION < QT_VERSION_CHECK(6, 12, 0)
 void QWaylandLayerSurface::setDesiredSize(const QSize &size)
 {
     const bool horizontallyConstrained = m_interface->anchors().testFlags({Window::AnchorLeft, Window::AnchorRight});
@@ -147,6 +148,22 @@ void QWaylandLayerSurface::setDesiredSize(const QSize &size)
     }
     set_size(effectiveSize.width(), effectiveSize.height());
 }
+#else
+void QWaylandLayerSurface::setDesiredSize(const QSizeF &size)
+{
+    const bool horizontallyConstrained = m_interface->anchors().testFlags({Window::AnchorLeft, Window::AnchorRight});
+    const bool verticallyConstrained = m_interface->anchors().testFlags({Window::AnchorTop, Window::AnchorBottom});
+
+    QSize effectiveSize = size.toSize();
+    if (horizontallyConstrained) {
+        effectiveSize.setWidth(0);
+    }
+    if (verticallyConstrained) {
+        effectiveSize.setHeight(0);
+    }
+    set_size(effectiveSize.width(), effectiveSize.height());
+}
+#endif
 
 void QWaylandLayerSurface::setAnchor(uint anchor)
 {
@@ -181,7 +198,11 @@ void QWaylandLayerSurface::setLayer(uint32_t layer)
         set_layer(layer);
 }
 
+#if QT_VERSION < QT_VERSION_CHECK(6, 12, 0)
 void QWaylandLayerSurface::setWindowSize(const QSize &size)
+#else
+void QWaylandLayerSurface::setWindowSize(const QSizeF &size)
+#endif
 {
     if (m_interface->desiredSize().isNull()) {
         setDesiredSize(size);
diff --git a/src/qwaylandlayersurface_p.h b/src/qwaylandlayersurface_p.h
index a48e522..9bb8474 100644
--- a/src/qwaylandlayersurface_p.h
+++ b/src/qwaylandlayersurface_p.h
@@ -34,7 +34,11 @@ public:
     }
     void attachPopup(QtWaylandClient::QWaylandShellSurface *popup) override;
 
+#if QT_VERSION < QT_VERSION_CHECK(6, 12, 0)
     void setDesiredSize(const QSize &size);
+#else
+    void setDesiredSize(const QSizeF &size);
+#endif
     void setAnchor(uint32_t anchor);
     void setExclusiveZone(int32_t zone);
     void setExclusiveEdge(uint32_t edge);
@@ -43,7 +47,11 @@ public:
     void setLayer(uint32_t layer);
 
     void applyConfigure() override;
+#if QT_VERSION < QT_VERSION_CHECK(6, 12, 0)
     void setWindowSize(const QSize &size) override;
+#else
+    void setWindowSize(const QSizeF &size) override;
+#endif
 
     bool requestActivate() override;
     bool requestActivateOnShow() override;