diff --git a/asminc/cx16.inc b/asminc/cx16.inc
index 268d701d6..1a916ecdb 100644
--- a/asminc/cx16.inc
+++ b/asminc/cx16.inc
@@ -538,11 +538,11 @@ NMIVec          := $0318
 ; YM2151 audio chip
 .struct YM2151
                 .org    $9F40
-  .union
-  STATUS        .byte
   ADDR          .byte
-  .endunion
+  .union
   DATA          .byte
+  STATUS        .byte
+  .endunion
 .endstruct
 
 ; X16 Emulator device
diff --git a/include/cx16.h b/include/cx16.h
index 42495c862..66f21843e 100644
--- a/include/cx16.h
+++ b/include/cx16.h
@@ -285,11 +285,11 @@ struct __vera {
 
 /* Audio chip */
 struct __ym2151 {
+    unsigned char       reg;            /* Register number for data */
     union {
-        unsigned char   reg;            /* Register number for data */
+        unsigned char   data;
         unsigned char   status;         /* Busy flag */
     };
-    unsigned char       data;
 };
 #define YM2151  (*(volatile struct __ym2151 *)0x9F40)