diff --git a/effects/backgroundcontrast/contrast.cpp b/effects/backgroundcontrast/contrast.cpp
index dbd9933fce..96ba3706a1 100644
--- a/effects/backgroundcontrast/contrast.cpp
+++ b/effects/backgroundcontrast/contrast.cpp
@@ -384,6 +384,8 @@ void ContrastEffect::doContrast(const QRegion& shape, const QRect& screen, const
 
     shader->bind();
 
+
+    shader->setOpacity(opacity);
     // Set up the texture matrix to transform from screen coordinates
     // to texture coordinates.
 #ifdef KWIN_HAVE_OPENGL_1
diff --git a/effects/backgroundcontrast/contrastshader.cpp b/effects/backgroundcontrast/contrastshader.cpp
index f814283fe8..472ca37c65 100644
--- a/effects/backgroundcontrast/contrastshader.cpp
+++ b/effects/backgroundcontrast/contrastshader.cpp
@@ -35,7 +35,7 @@ using namespace KWin;
 
 
 ContrastShader::ContrastShader()
-    : mValid(false), shader(NULL)
+    : mValid(false), shader(NULL), m_opacity(1)
 {
 }
 
@@ -93,6 +93,20 @@ bool ContrastShader::supported()
     return true;
 }
 
+void ContrastShader::setOpacity(float opacity)
+{
+    m_opacity = opacity;
+
+    ShaderManager::instance()->pushShader(shader);
+    shader->setUniform(opacityLocation, opacity);
+    ShaderManager::instance()->popShader();
+}
+
+float ContrastShader::opacity() const
+{
+    return m_opacity;
+}
+
 void ContrastShader::setColorMatrix(const QMatrix4x4 &matrix)
 {
     if (!isValid())
@@ -181,6 +195,7 @@ void ContrastShader::init()
 
     stream2 << "uniform mat4 colorMatrix;\n";
     stream2 << "uniform sampler2D sampler;\n";
+    stream2 << "uniform float opacity;\n";
     stream2 << "in vec4 varyingTexCoords;\n";
 
     if (glsl_140)
@@ -189,8 +204,16 @@ void ContrastShader::init()
     stream2 << "void main(void)\n";
     stream2 << "{\n";
     stream2 << "    vec4 tex = " << texture2D << "(sampler, varyingTexCoords.st);\n";
+    stream2 << "    mat4 identity = mat4(1.0, 0.0, 0.0, 0.0,\n";
+    stream2 << "                 0.0, 1.0, 0.0, 0.0,\n";
+    stream2 << "                 0.0, 0.0, 1.0, 0.0,\n";
+    stream2 << "                 0.0, 0.0, 0.0, 1.0);\n";
 
-    stream2 << "    "  << fragColor << " = tex * colorMatrix;\n";
+    stream2 << "    if (opacity >= 1.0) {\n";
+    stream2 << "        " << fragColor << " = tex * colorMatrix;\n";
+    stream2 << "    } else {\n";
+    stream2 << "        " << fragColor << " = tex * (opacity * colorMatrix + (1-opacity) * identity);\n";
+    stream2 << "    }\n";
 
     stream2 << "}\n";
     stream2.flush();
@@ -201,6 +224,7 @@ void ContrastShader::init()
         colorMatrixLocation = shader->uniformLocation("colorMatrix");
         textureMatrixLocation = shader->uniformLocation("textureMatrix");
         mvpMatrixLocation     = shader->uniformLocation("modelViewProjectionMatrix");
+        opacityLocation       = shader->uniformLocation("opacity");
 
         QMatrix4x4 modelViewProjection;
         modelViewProjection.ortho(0, displayWidth(), displayHeight(), 0, 0, 65535);
@@ -208,6 +232,7 @@ void ContrastShader::init()
         shader->setUniform(colorMatrixLocation, QMatrix4x4());
         shader->setUniform(textureMatrixLocation, QMatrix4x4());
         shader->setUniform(mvpMatrixLocation, modelViewProjection);
+        shader->setUniform(opacityLocation, (float)1.0);
         ShaderManager::instance()->popShader();
     }
 
diff --git a/effects/backgroundcontrast/contrastshader.h b/effects/backgroundcontrast/contrastshader.h
index cf8de81bf5..c36baed227 100644
--- a/effects/backgroundcontrast/contrastshader.h
+++ b/effects/backgroundcontrast/contrastshader.h
@@ -52,6 +52,9 @@ public:
 
     static bool supported();
 
+    void setOpacity(float opacity);
+    float opacity() const;
+
 protected:
     void setIsValid(bool value) {
         mValid = value;
@@ -65,6 +68,8 @@ private:
     int textureMatrixLocation;
     int colorMatrixLocation;
     int pixelSizeLocation;
+    int opacityLocation;
+    float m_opacity;
 };