diff --git a/src/plasma/private/theme_p.cpp b/src/plasma/private/theme_p.cpp
--- a/src/plasma/private/theme_p.cpp
+++ b/src/plasma/private/theme_p.cpp
@@ -71,9 +71,9 @@
       useGlobal(true),
       hasWallpapers(false),
       fixedName(false),
-      backgroundContrast(0),
-      backgroundIntensity(0),
-      backgroundSaturation(0),
+      backgroundContrast(qQNaN()),
+      backgroundIntensity(qQNaN()),
+      backgroundSaturation(qQNaN()),
       backgroundContrastEnabled(true),
       apiMajor(1),
       apiMinor(0),
@@ -728,23 +728,9 @@
         cg = KConfigGroup(metadata, "ContrastEffect");
         backgroundContrastEnabled = cg.readEntry("enabled", false);
 
-        //if (backgroundContrastEnabled) {
-        // Make up sensible default values, based on the background color
-        // This works for a light theme -- lighting up the background
-        qreal _contrast = 0.3;
-        qreal _intensity = 1.9;
-        qreal _saturation = 1.7;
-
-        // If we're using a dark background color, darken the background
-        if (qGray(color(Plasma::Theme::BackgroundColor).rgb()) < 127) {
-            _contrast = 0.45;
-            _intensity = 0.45;
-            _saturation = 1.7;
-        }
-        backgroundContrast = cg.readEntry("contrast", _contrast);
-        backgroundIntensity = cg.readEntry("intensity", _intensity);
-        backgroundSaturation = cg.readEntry("saturation", _saturation);
-        //}
+        backgroundContrast = cg.readEntry("contrast", qQNaN());
+        backgroundIntensity = cg.readEntry("intensity", qQNaN());
+        backgroundSaturation = cg.readEntry("saturation", qQNaN());
     } else {
         backgroundContrastEnabled = false;
     }
diff --git a/src/plasma/theme.cpp b/src/plasma/theme.cpp
--- a/src/plasma/theme.cpp
+++ b/src/plasma/theme.cpp
@@ -477,16 +477,36 @@
 
 qreal Theme::backgroundContrast() const
 {
+    if (qIsNaN(d->backgroundContrast)) {
+        // Make up sensible default values, based on the background color
+        // If we're using a dark background color, darken the background
+        if (qGray(color(Plasma::Theme::BackgroundColor).rgb()) < 127) {
+            return 0.45;
+        // for a light theme lighten up the background
+        } else {
+            return 0.3;
+        }
+    }
     return d->backgroundContrast;
 }
 
 qreal Theme::backgroundIntensity() const
 {
+    if (qIsNaN(d->backgroundIntensity)) {
+        if (qGray(color(Plasma::Theme::BackgroundColor).rgb()) < 127) {
+            return 0.45;
+        } else {
+            return 1.9;
+        }
+    }
     return d->backgroundIntensity;
 }
 
 qreal Theme::backgroundSaturation() const
 {
+    if (qIsNaN(d->backgroundSaturation)) {
+        return 1.7;
+    }
     return d->backgroundSaturation;
 }