diff --git a/src/AllPlot.cpp b/src/AllPlot.cpp
index 350de707a..4c7bad8cb 100644
--- a/src/AllPlot.cpp
+++ b/src/AllPlot.cpp
@@ -432,7 +432,7 @@ AllPlotObject::setColor(QColor color)
 
         // lighten up for the next guy
         color = color.darker(110);
-        alpha -= 10;
+        if (alpha > 10) alpha -= 10;
     }
 
     // has to be different...