diff --git a/MagickCore/cache-private.h b/MagickCore/cache-private.h
index 26a38dc..e5b6bf3 100644
--- a/MagickCore/cache-private.h
+++ b/MagickCore/cache-private.h
@@ -175,6 +175,7 @@
     *random_info;
 
   MagickBooleanType
+    synchronize,
     debug;
 
   MagickThreadType