Eliminate compiler warnings
diff --git a/MagickCore/effect.c b/MagickCore/effect.c
index 48a2adf..5a33212 100644
--- a/MagickCore/effect.c
+++ b/MagickCore/effect.c
@@ -2942,7 +2942,7 @@
           }
         gamma=0.0;
         pixel=0.0;
-        if ((GetPixelChannelTraits(image,AlphaChannel) == UndefinedPixelTrait) ||
+        if ((GetPixelChannelTraits(image,AlphaPixelChannel) == UndefinedPixelTrait) ||
             (channel == AlphaPixelChannel))
           {
             for (j=0; j < (ssize_t) n; j+=(ssize_t) step)