diff --git a/Engine/ViewerInstance.cpp b/Engine/ViewerInstance.cpp
index 9260825b5c..1f1b28552a 100644
--- a/Engine/ViewerInstance.cpp
+++ b/Engine/ViewerInstance.cpp
@@ -2098,7 +2098,7 @@ findAutoContrastVminVmax_generic(const ImagePtr inputImage,
                 maxi = std::max(std::max(r, g), b);
                 break;
             case eDisplayChannelsY:
-                mini = r = 0.299 * r + 0.587 * g + 0.114 * b;
+                mini = 0.299 * r + 0.587 * g + 0.114 * b;
                 maxi = mini;
                 break;
             case eDisplayChannelsR: