diff --git a/src/window.cpp b/src/window.cpp
index d81ffc9b7c..7c4310ec33 100644
--- a/src/window.cpp
+++ b/src/window.cpp
@@ -4225,15 +4225,6 @@ void Window::checkOffscreenPosition(QRectF *geom, const QRectF &screenArea)
     }
 }
 
-/**
- * Returns the natural size of the window, if the window is not shaded it's the same
- * as size().
- */
-QSizeF Window::implicitSize() const
-{
-    return clientSizeToFrameSize(clientSize());
-}
-
 /**
  * Constrains the client size @p size according to a set of the window's size hints.
  *
diff --git a/src/window.h b/src/window.h
index 16b3cadb20..d8386d416a 100644
--- a/src/window.h
+++ b/src/window.h
@@ -1147,7 +1147,6 @@ public:
 
     virtual QSizeF constrainClientSize(const QSizeF &size, SizeMode mode = SizeModeAny) const;
     QSizeF constrainFrameSize(const QSizeF &size, SizeMode mode = SizeModeAny) const;
-    QSizeF implicitSize() const;
 
     /**
      * Calculates the matching client position for the given frame position @p point.
diff --git a/src/x11window.cpp b/src/x11window.cpp
index b159ceedef..6eb0f6daf8 100644
--- a/src/x11window.cpp
+++ b/src/x11window.cpp
@@ -1156,7 +1156,7 @@ void X11Window::createDecoration(const QRectF &oldgeom)
     }
     setDecoration(decoration);
 
-    moveResize(QRectF(calculateGravitation(false), implicitSize()));
+    moveResize(QRectF(calculateGravitation(false), clientSizeToFrameSize(clientSize())));
     maybeCreateX11DecorationRenderer();
     Q_EMIT geometryShapeChanged(this, oldgeom);
 }
@@ -1168,7 +1168,7 @@ void X11Window::destroyDecoration()
         QPointF grav = calculateGravitation(true);
         setDecoration(nullptr);
         maybeDestroyX11DecorationRenderer();
-        moveResize(QRectF(grav, implicitSize()));
+        moveResize(QRectF(grav, clientSizeToFrameSize(clientSize())));
         if (!isZombie()) {
             Q_EMIT geometryShapeChanged(this, oldgeom);
         }
@@ -2697,6 +2697,15 @@ QRectF X11Window::frameRectToBufferRect(const QRectF &rect) const
     return frameRectToClientRect(rect);
 }
 
+/**
+ * Returns the natural size of the window, if the window is not shaded it's the same
+ * as size().
+ */
+QSizeF X11Window::implicitSize() const
+{
+    return clientSizeToFrameSize(m_client.geometry().size());
+}
+
 QMatrix4x4 X11Window::inputTransformation() const
 {
     QMatrix4x4 matrix;
diff --git a/src/x11window.h b/src/x11window.h
index b9bca1615e..b0a9a648b0 100644
--- a/src/x11window.h
+++ b/src/x11window.h
@@ -110,6 +110,7 @@ public:
     QSizeF frameSizeToClientSize(const QSizeF &size) const override;
     QSizeF clientSizeToFrameSize(const QSizeF &size) const override;
     QRectF frameRectToBufferRect(const QRectF &rect) const;
+    QSizeF implicitSize() const;
 
     QMatrix4x4 inputTransformation() const override;