diff --git a/include/decompress.h b/include/decompress.h
index d10c2510b..8d46fb16a 100644
--- a/include/decompress.h
+++ b/include/decompress.h
@@ -3,10 +3,17 @@
 
 #include "file_system.h"
 
+// size: 0x8
+typedef struct SiroArchive
+{
+    /* 0x0 */ u32 magic;
+    /* 0x4 */ const void *data;
+} SiroArchive;
+
 u32 DecompressAT(u8 *dst, s32 dstLen, const u8 *src);
 u32 DecompressATFile(void *dst, s32 dstLen, OpenedFile *file);
 u32 DecompressATGlobalFile(u32 *result, s32 resultLength, OpenedFile *file);
-const u8 *GetSiroPtr(OpenedFile *openedFile);
+const void *GetSiroPtr(OpenedFile *openedFile);
 void nullsub_16(void);
 
 // Returns FALSE if the ascii chars in both strings match, ignoring uppercase/lowercase differences.
diff --git a/include/file_system.h b/include/file_system.h
index ffa5b6ccb..a6c4e91b3 100644
--- a/include/file_system.h
+++ b/include/file_system.h
@@ -5,14 +5,14 @@
 typedef struct File
 {
     /* 0x0 */ char *name;
-    /* 0x4 */ const u8 *data;
+    /* 0x4 */ const void *data;
 } File;
 
 // size: 0x8
 typedef struct OpenedFile
 {
     /* 0x0 */ const File *file;
-    /* 0x4 */ const u8 *data;
+    /* 0x4 */ const void *data;
 } OpenedFile;
 
 // size: 0x10
@@ -23,13 +23,6 @@ typedef struct FileArchive
     /* 0xC */ const File *entries;
 } FileArchive;
 
-// size: 0x8
-typedef struct SiroArchive
-{
-    /* 0x0 */ u32 magic;
-    /* 0x4 */ u8 *data;
-} SiroArchive;
-
 // size: 0x8
 typedef struct UnkFileStruct
 {
diff --git a/src/code_803E724.c b/src/code_803E724.c
index 85dcfaddc..8ec594e19 100644
--- a/src/code_803E724.c
+++ b/src/code_803E724.c
@@ -514,7 +514,7 @@ s32 sub_803EF90(s32 a0, u8 a1)
         bitsNo = 0;
         for (id = 0; id < 4; id++) {
             u32 *dst = mainDst;
-            const u32 *src = (u32 *)((&gUnknown_202EC9C->data[4] + r12[id] * 32));
+            const u32 *src = (u32 *)((&((u8 *)gUnknown_202EC9C->data)[4] + r12[id] * 32));
 
             for (i = 0; i < 8; i++) {
                 u32 toOr1, toOr2;
@@ -546,13 +546,13 @@ s32 sub_803EF90(s32 a0, u8 a1)
     if (a0 > 999) a0 = 999;
     if (a0 < -999) a0 = -999;
 
-    r2 = (u32 *)(gUnknown_202EC9C->data + 0x184);
+    r2 = (u32 *)((u8 *)gUnknown_202EC9C->data + 0x184);
     if (a1) {
         if (a0 > 0) {
-            r2 = (u32 *)(gUnknown_202EC9C->data + 0x144);
+            r2 = (u32 *)((u8 *)gUnknown_202EC9C->data + 0x144);
         }
         else if (a0 < 0) {
-            r2 = (u32 *)(gUnknown_202EC9C->data + 0x164);
+            r2 = (u32 *)((u8 *)gUnknown_202EC9C->data + 0x164);
             a0 = -a0;
         }
     }
@@ -608,7 +608,7 @@ s32 sub_803EF90(s32 a0, u8 a1)
         }
 
         if (arrId == 9 && unkBool) {
-            const u32 *src = (u32 *)(&gUnknown_202EC9C->data[4]);
+            const u32 *src = (u32 *)(&((u8 *)gUnknown_202EC9C->data)[4]);
             u32 *dst = mainDst;
             for (i = 0; i < 8; i++) {
                 u32 toOr1, toOr2;
@@ -638,7 +638,7 @@ s32 sub_803EF90(s32 a0, u8 a1)
     }
 
     {
-        const u32 *src = (u32 *)(&gUnknown_202EC9C->data[4] + (a0 * 32));
+        const u32 *src = (u32 *)(&((u8 *)gUnknown_202EC9C->data)[4] + (a0 * 32));
         u32 *dst = mainDst;
         for (i = 0; i < 8; i++) {
             u32 toOr1, toOr2;
diff --git a/src/decompress.c b/src/decompress.c
index ea980ee5d..244f86dbb 100644
--- a/src/decompress.c
+++ b/src/decompress.c
@@ -17,11 +17,11 @@ static void DecompressAT_Finish(void);
 static char DecompressAT_GetByte(s32);
 static void DecompressAT_Init(u32 *);
 static u32 DecompressATGlobal(u32 *, s32, const char *);
-static void NDS_DecompressRLE(const void *);
+static void NDS_DecompressRLE(const SiroArchive *);
 
-const u8 *GetSiroPtr(OpenedFile *openedFile)
+const void *GetSiroPtr(OpenedFile *openedFile)
 {
-    struct SiroArchive *siro = (struct SiroArchive *)openedFile->data;
+    const SiroArchive *siro = (const SiroArchive *)openedFile->data;
 
     if (siro->magic == MAGIC_SIR0)
         NDS_DecompressRLE(openedFile->data);
@@ -33,7 +33,7 @@ const u8 *GetSiroPtr(OpenedFile *openedFile)
     return openedFile->data;
 }
 
-UNUSED static void *UnusedGetSir0Ptr(struct SiroArchive *siro)
+UNUSED static const void *UnusedGetSir0Ptr(const SiroArchive *siro)
 {
     if (siro->magic != MAGIC_SIR0)
         return siro;
@@ -42,7 +42,7 @@ UNUSED static void *UnusedGetSir0Ptr(struct SiroArchive *siro)
     return siro->data;
 }
 
-static void NDS_DecompressRLE(const void *unused)
+static void NDS_DecompressRLE(const SiroArchive *siro)
 {
 }