diff --git a/d2x-rebirth/main/piggy.c b/d2x-rebirth/main/piggy.c
index 091469645..88e09a836 100644
--- a/d2x-rebirth/main/piggy.c
+++ b/d2x-rebirth/main/piggy.c
@@ -130,6 +130,7 @@ typedef struct DiskBitmapHeader {
 	ubyte avg_color;
 	int offset;
 } __pack__ DiskBitmapHeader;
+typedef char padding_check[sizeof(DiskBitmapHeader) == 0x12 ? 1 : -1];
 
 #define DISKBITMAPHEADER_D1_SIZE 17 // no wh_extra