diff --git a/MagickCore/cache-private.h b/MagickCore/cache-private.h
index bfceb8c..92fc0f0 100644
--- a/MagickCore/cache-private.h
+++ b/MagickCore/cache-private.h
@@ -119,7 +119,8 @@
     colorspace;
 
   MagickBooleanType
-    matte;
+    matte,
+    masky;
 
   size_t
     columns,