diff --git a/src/decorations/decorationrenderer.cpp b/src/decorations/decorationrenderer.cpp
index 9a4506ffad..58d12a1100 100644
--- a/src/decorations/decorationrenderer.cpp
+++ b/src/decorations/decorationrenderer.cpp
@@ -80,7 +80,7 @@ QImage Renderer::renderToImage(const QRect &geo)
     image.fill(Qt::transparent);
     QPainter p(&image);
     p.setRenderHint(QPainter::Antialiasing);
-    p.setWindow(QRect(geo.topLeft(), geo.size() * dpr));
+    p.setWindow(QRect(geo.topLeft(), geo.size() * qPainterEffectiveDevicePixelRatio(&p)));
     p.setClipRect(geo);
     renderToPainter(&p, geo);
     return image;
diff --git a/src/plugins/scenes/opengl/scene_opengl.cpp b/src/plugins/scenes/opengl/scene_opengl.cpp
index 350701524c..c96e2c21a1 100644
--- a/src/plugins/scenes/opengl/scene_opengl.cpp
+++ b/src/plugins/scenes/opengl/scene_opengl.cpp
@@ -2644,7 +2644,7 @@ void SceneOpenGLDecorationRenderer::render()
         QPainter painter(&image);
         painter.setRenderHint(QPainter::Antialiasing);
         painter.setViewport(QRect(viewport.topLeft(), viewport.size() * devicePixelRatio));
-        painter.setWindow(QRect(geo.topLeft(), geo.size() * devicePixelRatio));
+        painter.setWindow(QRect(geo.topLeft(), geo.size() * qPainterEffectiveDevicePixelRatio(&painter)));
         painter.setClipRect(geo);
         renderToPainter(&painter, geo);
         painter.end();
diff --git a/src/plugins/scenes/qpainter/scene_qpainter.cpp b/src/plugins/scenes/qpainter/scene_qpainter.cpp
index 6b477b3446..3b75f93808 100644
--- a/src/plugins/scenes/qpainter/scene_qpainter.cpp
+++ b/src/plugins/scenes/qpainter/scene_qpainter.cpp
@@ -774,7 +774,7 @@ void SceneQPainterDecorationRenderer::render()
         }
         QPainter painter(&m_images[index]);
         painter.setRenderHint(QPainter::Antialiasing);
-        painter.setWindow(QRect(partRect.topLeft(), partRect.size() * m_images[index].devicePixelRatio()));
+        painter.setWindow(QRect(partRect.topLeft(), partRect.size() * qPainterEffectiveDevicePixelRatio(&painter)));
         painter.setClipRect(rect);
         painter.save();
         // clear existing part
diff --git a/src/utils.cpp b/src/utils.cpp
index adc45ddd86..3a627904d7 100644
--- a/src/utils.cpp
+++ b/src/utils.cpp
@@ -16,6 +16,7 @@
 
 #include "utils.h"
 
+#include <QPainter>
 #include <QWidget>
 #include <kkeyserver.h>
 
@@ -195,6 +196,11 @@ Qt::KeyboardModifiers x11ToQtKeyboardModifiers(int state)
     return ret;
 }
 
+qreal qPainterEffectiveDevicePixelRatio(const QPainter *painter)
+{
+    return std::max(qreal(1), painter->device()->devicePixelRatioF());
+}
+
 } // namespace
 
 #ifndef KCMRULES
diff --git a/src/utils.h b/src/utils.h
index c663ff8ad1..50f7e98141 100644
--- a/src/utils.h
+++ b/src/utils.h
@@ -119,6 +119,15 @@ void KWIN_EXPORT ungrabXServer();
 bool KWIN_EXPORT grabXKeyboard(xcb_window_t w = XCB_WINDOW_NONE);
 void KWIN_EXPORT ungrabXKeyboard();
 
+/**
+ * QPainter::setWindow() doesn't work as expected when the device pixel ratio of the paint
+ * device is less than 1.
+ *
+ * QPainter simply doesn't allow the effective scale factor to be less than 1. Use this function
+ * to determine the effective device pixel ratio by which the window rect has to be scaled.
+ */
+qreal KWIN_EXPORT qPainterEffectiveDevicePixelRatio(const QPainter *painter);
+
 /**
  * Small helper class which performs grabXServer in the ctor and
  * ungrabXServer in the dtor. Use this class to ensure that grab and