diff --git a/include/functions.h b/include/functions.h
index 26d8ee6090..946fa16df0 100644
--- a/include/functions.h
+++ b/include/functions.h
@@ -29,7 +29,7 @@ void ViConfig_UpdateVi(u32 black);
 void ViConfig_UpdateBlack(void);
 void* Yaz0_FirstDMA(void);
 void* Yaz0_NextDMA(u8* curSrcPos);
-void Yaz0_DecompressImpl(Yaz0Header* hdr, u8* dst);
+void Yaz0_DecompressImpl(u8* src, u8* dst);
 void Yaz0_Decompress(uintptr_t romStart, u8* dst, size_t size);
 void Locale_Init(void);
 void Locale_ResetRegion(void);
@@ -45,7 +45,7 @@ void* is_proutSyncPrintf(void* arg, const char* str, size_t count);
 NORETURN void func_80002384(const char* exp, const char* file, u32 line);
 #endif
 OSPiHandle* osDriveRomInit(void);
-void Mio0_Decompress(Yaz0Header* hdr, u8* dst);
+void Mio0_Decompress(u8* src, u8* dst);
 void StackCheck_Init(StackEntry* entry, void* stackBottom, void* stackTop, u32 initValue, s32 minSpace,
                      const char* name);
 void StackCheck_Cleanup(StackEntry* entry);
diff --git a/include/z64.h b/include/z64.h
index 09d205d5ee..976d932cce 100644
--- a/include/z64.h
+++ b/include/z64.h
@@ -695,8 +695,7 @@ typedef struct {
     /* 0x04 */ u32 decSize;
     /* 0x08 */ u32 compInfoOffset; // only used in mio0
     /* 0x0C */ u32 uncompDataOffset; // only used in mio0
-    /* 0x10 */ u8 data[1];
-} Yaz0Header; // size = 0x10 ("data" is not part of the header)
+} Yaz0Header; // size = 0x10
 
 struct ArenaNode;
 
diff --git a/src/boot/yaz0.c b/src/boot/yaz0.c
index 80d8509280..448ab38350 100644
--- a/src/boot/yaz0.c
+++ b/src/boot/yaz0.c
@@ -48,16 +48,18 @@ void* Yaz0_NextDMA(u8* curSrcPos) {
     return dst;
 }
 
-void Yaz0_DecompressImpl(Yaz0Header* hdr, u8* dst) {
+void Yaz0_DecompressImpl(u8* src, u8* dst) {
+    Yaz0Header* header = (Yaz0Header*)src;
     u32 bitIdx = 0;
-    u8* src = hdr->data;
-    u8* dstEnd = dst + hdr->decSize;
+    u8* dstEnd = dst + header->decSize;
     u32 chunkHeader;
     u32 nibble;
     u8* backPtr;
     u32 chunkSize;
     u32 off;
 
+    src += sizeof(Yaz0Header);
+
     do {
         if (bitIdx == 0) {
             if ((sYaz0MaxPtr < src) && (sYaz0CurSize != 0)) {