Moved aliases to coder header file.
diff --git a/coders/null.h b/coders/null.h
index 06063b4..cf177df 100644
--- a/coders/null.h
+++ b/coders/null.h
@@ -18,6 +18,8 @@
 
 #define MagickNULLHeaders
 
+#define MagickNULLAliases
+
 #if defined(__cplusplus) || defined(c_plusplus)
 extern "C" {
 #endif