diff --git a/include/arm9/dev.h b/include/arm9/dev.h
index f24266f..6db1b34 100644
--- a/include/arm9/dev.h
+++ b/include/arm9/dev.h
@@ -7,7 +7,7 @@
 	bool initialized;
 	bool (*init)();
 	bool (*read)(u32 offset, u32 size, void *buf);
-	bool (*write)(u32 offset, u32 size, void *buf);
+	bool (*write)(u32 offset, u32 size, const void *buf);
 	bool (*close)();
 	bool (*is_active)();
 	
diff --git a/include/arm9/sdmmc.h b/include/arm9/sdmmc.h
index 6e9023b..6322c39 100644
--- a/include/arm9/sdmmc.h
+++ b/include/arm9/sdmmc.h
@@ -122,11 +122,11 @@
 	void sdmmc_init();
 	int sdmmc_sdcard_readsector(uint32_t sector_no, uint8_t *out);
 	int sdmmc_sdcard_readsectors(uint32_t sector_no, uint32_t numsectors, uint8_t *out);
-	int sdmmc_sdcard_writesector(uint32_t sector_no, uint8_t *in);
-	int sdmmc_sdcard_writesectors(uint32_t sector_no, uint32_t numsectors, uint8_t *in);
+	int sdmmc_sdcard_writesector(uint32_t sector_no, const uint8_t *in);
+	int sdmmc_sdcard_writesectors(uint32_t sector_no, uint32_t numsectors, const uint8_t *in);
 	
 	int sdmmc_nand_readsectors(uint32_t sector_no, uint32_t numsectors, uint8_t *out);
-	int sdmmc_nand_writesectors(uint32_t sector_no, uint32_t numsectors, uint8_t *in);
+	int sdmmc_nand_writesectors(uint32_t sector_no, uint32_t numsectors, const uint8_t *in);
 	
 	mmcdevice *getMMCDevice(int drive);
 	
diff --git a/source/arm9/dev.c b/source/arm9/dev.c
index 19b3312..5ff72d0 100644
--- a/source/arm9/dev.c
+++ b/source/arm9/dev.c
@@ -12,7 +12,7 @@
 // SD card device
 bool sdmmc_sd_init(void);
 bool sdmmc_sd_read(u32 offset, u32 size, void *buf);
-bool sdmmc_sd_write(u32 offset, u32 size, void *buf);
+bool sdmmc_sd_write(u32 offset, u32 size, const void *buf);
 bool sdmmc_sd_close(void);
 bool sdmmc_sd_is_active(void);
 
@@ -30,7 +30,7 @@
 // Raw NAND device
 bool sdmmc_rnand_init(void);
 bool sdmmc_rnand_read(u32 offset, u32 size, void *buf);
-bool sdmmc_rnand_write(u32 offset, u32 size, void *buf);
+bool sdmmc_rnand_write(u32 offset, u32 size, const void *buf);
 bool sdmmc_rnand_close(void);
 bool sdmmc_rnand_is_active(void);
 
@@ -64,7 +64,7 @@
 
 bool sdmmc_dnand_init(void);
 bool sdmmc_dnand_read(u32 offset, u32 size, void *buf);
-bool sdmmc_dnand_write(u32 offset, u32 size, void *buf);
+bool sdmmc_dnand_write(u32 offset, u32 size, const void *buf);
 bool sdmmc_dnand_close(void);
 bool sdmmc_dnand_is_active(void);
 
@@ -123,7 +123,7 @@
 	return !sdmmc_sdcard_readsectors(offset >> 9, size >> 9, buf);
 }
 
-bool sdmmc_sd_write(u32 offset, u32 size, void *buf)
+bool sdmmc_sd_write(u32 offset, u32 size, const void *buf)
 {
 	if(!dev_sd.initialized)
 		return false;
@@ -162,7 +162,7 @@
 	return !sdmmc_nand_readsectors(offset >> 9, size >> 9, buf);
 }
 
-bool sdmmc_rnand_write(u32 offset, u32 size, void *buf)
+bool sdmmc_rnand_write(u32 offset, u32 size, const void *buf)
 {
 	if(!dev_rnand.initialized)
 		return false;
@@ -309,7 +309,7 @@
 	return true;
 }
 
-bool sdmmc_dnand_write(u32 offset, u32 size, void *buf)
+bool sdmmc_dnand_write(u32 offset, u32 size, const void *buf)
 {
 	if(!dev_dnand.dev.initialized)
 		return false;
diff --git a/source/arm9/sdmmc.c b/source/arm9/sdmmc.c
index 85d0329..4909802 100644
--- a/source/arm9/sdmmc.c
+++ b/source/arm9/sdmmc.c
@@ -215,7 +215,7 @@
 	}
 }
 
-int sdmmc_sdcard_writesectors(uint32_t sector_no, uint32_t numsectors, uint8_t *in)
+int sdmmc_sdcard_writesectors(uint32_t sector_no, uint32_t numsectors, const uint8_t *in)
 {
 	if(handleSD.isSDHC == 0) sector_no <<= 9;
 	inittarget(&handleSD);
@@ -225,7 +225,7 @@
 	sdmmc_write16(REG_SDBLKLEN32,0x200);
 #endif
 	sdmmc_write16(REG_SDBLKCOUNT,numsectors);
-	handleSD.data = in;
+	handleSD.data = (uint8_t*) in;
 	handleSD.size = numsectors << 9;
 	sdmmc_send_command(&handleSD,0x52C19,sector_no);
 	return geterror(&handleSD);
@@ -264,7 +264,7 @@
 	return geterror(&handleNAND);
 }
 
-int sdmmc_nand_writesectors(uint32_t sector_no, uint32_t numsectors, uint8_t *in) //experimental
+int sdmmc_nand_writesectors(uint32_t sector_no, uint32_t numsectors, const uint8_t *in) //experimental
 {
 	if(handleNAND.isSDHC == 0) sector_no <<= 9;
 	inittarget(&handleNAND);
@@ -274,7 +274,7 @@
 	sdmmc_write16(REG_SDBLKLEN32,0x200);
 #endif
 	sdmmc_write16(REG_SDBLKCOUNT,numsectors);
-	handleNAND.data = in;
+	handleNAND.data = (uint8_t*) in;
 	handleNAND.size = numsectors << 9;
 	sdmmc_send_command(&handleNAND,0x52C19,sector_no);
 	inittarget(&handleSD);