diff --git a/effects/cube/cube.cpp b/effects/cube/cube.cpp
index 2e5fdf9eea..943a766143 100644
--- a/effects/cube/cube.cpp
+++ b/effects/cube/cube.cpp
@@ -901,6 +901,7 @@ void CubeEffect::paintCap(bool frontFirst, float zOffset)
         capShader = true;
         ShaderManager::instance()->pushShader(m_capShader);
         m_capShader->setUniform("u_opacity", cubeOpacity);
+        m_capShader->setUniform("u_mirror", 1);
         if (reflectionPainting) {
             m_capShader->setUniform("screenTransformation", m_reflectionMatrix*m_rotationMatrix);
         } else {
@@ -970,6 +971,7 @@ void CubeEffect::paintCap(bool frontFirst, float zOffset)
     capMatrix.translate(0.0, -rect.height(), 0.0);
     if (capShader) {
         m_capShader->setUniform("windowTransformation", capMatrix);
+        m_capShader->setUniform("u_mirror", 0);
     } else {
 #ifndef KWIN_HAVE_OPENGLES
         glMatrixMode( GL_TEXTURE );
diff --git a/effects/cube/data/cube-cap.glsl b/effects/cube/data/cube-cap.glsl
index a3d6959d00..f106ea46e8 100644
--- a/effects/cube/data/cube-cap.glsl
+++ b/effects/cube/data/cube-cap.glsl
@@ -1,14 +1,24 @@
 uniform sampler2D sample;
 uniform vec4 u_capColor;
 uniform float u_opacity;
+uniform int u_mirror;
 
 varying vec2 varyingTexCoords;
 
+vec2 mirrorTex(vec2 coords) {
+    vec2 mirrored = coords;
+    if (u_mirror != 0) {
+        mirrored.t = mirrored.t * (-1.0) + 1.0;
+    }
+    return mirrored;
+}
+
 void main() {
     vec4 color = u_capColor;
-    vec4 tex = texture2D(sample, varyingTexCoords);
-    if (varyingTexCoords.s < 0.0 || varyingTexCoords.s > 1.0 ||
-            varyingTexCoords.t < 0.0 || varyingTexCoords.t > 1.0) {
+    vec2 texCoord = mirrorTex(varyingTexCoords);
+    vec4 tex = texture2D(sample, texCoord);
+    if (texCoord.s < 0.0 || texCoord.s > 1.0 ||
+            texCoord.t < 0.0 || texCoord.t > 1.0) {
         tex = u_capColor;
     }
     color.rgb = tex.rgb*tex.a + color.rgb*(1.0-tex.a);