diff --git a/plugins/scenes/opengl/scene_opengl.h b/plugins/scenes/opengl/scene_opengl.h
--- a/plugins/scenes/opengl/scene_opengl.h
+++ b/plugins/scenes/opengl/scene_opengl.h
@@ -173,6 +173,8 @@
     bool m_hardwareClipping;
 };
 
+class OpenGLWindowPixmap;
+
 class SceneOpenGL2Window : public SceneOpenGL::Window
 {
 public:
@@ -209,6 +211,7 @@
     virtual void performPaint(int mask, QRegion region, WindowPaintData data);
 
 private:
+    void renderSubSurface(GLShader *shader, const QMatrix4x4 &mvp, const QMatrix4x4 &windowMatrix, OpenGLWindowPixmap *pixmap, const QRegion &region, bool hardwareClipping);
     /**
      * Whether prepareStates enabled blending and restore states should disable again.
      **/
diff --git a/plugins/scenes/opengl/scene_opengl.cpp b/plugins/scenes/opengl/scene_opengl.cpp
--- a/plugins/scenes/opengl/scene_opengl.cpp
+++ b/plugins/scenes/opengl/scene_opengl.cpp
@@ -47,6 +47,7 @@
 #include "decorations/decoratedclient.h"
 #include <logging.h>
 
+#include <KWayland/Server/buffer_interface.h>
 #include <KWayland/Server/subcompositor_interface.h>
 #include <KWayland/Server/surface_interface.h>
 
@@ -1358,7 +1359,7 @@
     return scene->projectionMatrix() * mvMatrix;
 }
 
-static void renderSubSurface(GLShader *shader, const QMatrix4x4 &mvp, const QMatrix4x4 &windowMatrix, OpenGLWindowPixmap *pixmap, const QRegion &region, bool hardwareClipping)
+void SceneOpenGL2Window::renderSubSurface(GLShader *shader, const QMatrix4x4 &mvp, const QMatrix4x4 &windowMatrix, OpenGLWindowPixmap *pixmap, const QRegion &region, bool hardwareClipping)
 {
     QMatrix4x4 newWindowMatrix = windowMatrix;
     newWindowMatrix.translate(pixmap->subSurface()->position().x(), pixmap->subSurface()->position().y());
@@ -1369,6 +1370,7 @@
     }
 
     if (!pixmap->texture()->isNull()) {
+        setBlendEnabled(pixmap->buffer() && pixmap->buffer()->hasAlphaChannel());
         // render this texture
         shader->setUniform(GLShader::ModelViewProjectionMatrix, mvp * newWindowMatrix);
         auto texture = pixmap->texture();
@@ -1515,8 +1517,6 @@
 
     vbo->unbindArrays();
 
-    setBlendEnabled(false);
-
     // render sub-surfaces
     auto wp = windowPixmap<OpenGLWindowPixmap>();
     const auto &children = wp ? wp->children() : QVector<WindowPixmap*>();
@@ -1528,6 +1528,8 @@
         renderSubSurface(shader, modelViewProjection, windowMatrix, static_cast<OpenGLWindowPixmap*>(pixmap), region, m_hardwareClipping);
     }
 
+    setBlendEnabled(false);
+
     if (!data.shader)
         ShaderManager::instance()->popShader();