diff --git a/fs/ext4/ext4_common.c b/fs/ext4/ext4_common.c
index 29308e3..e912378 100644
--- a/fs/ext4/ext4_common.c
+++ b/fs/ext4/ext4_common.c
@@ -190,7 +190,7 @@
 	return res;
 }
 
-void put_ext4(uint64_t off, void *buf, uint32_t size)
+void put_ext4(uint64_t off, const void *buf, uint32_t size)
 {
 	uint64_t startblock;
 	uint64_t remainder;
diff --git a/fs/ext4/ext4_common.h b/fs/ext4/ext4_common.h
index 1ee81ab..4dff191 100644
--- a/fs/ext4/ext4_common.h
+++ b/fs/ext4/ext4_common.h
@@ -72,7 +72,7 @@
 void ext4fs_allocate_blocks(struct ext2_inode *file_inode,
 				unsigned int total_remaining_blocks,
 				unsigned int *total_no_of_block);
-void put_ext4(uint64_t off, void *buf, uint32_t size);
+void put_ext4(uint64_t off, const void *buf, uint32_t size);
 struct ext2_block_group *ext4fs_get_group_descriptor
 	(const struct ext_filesystem *fs, uint32_t bg_idx);
 uint64_t ext4fs_bg_get_block_id(const struct ext2_block_group *bg,
diff --git a/fs/ext4/ext4_write.c b/fs/ext4/ext4_write.c
index 95ffa3d..b5b7ee8 100644
--- a/fs/ext4/ext4_write.c
+++ b/fs/ext4/ext4_write.c
@@ -752,7 +752,7 @@
  * contigous sectors as ext4fs_read_file
  */
 static int ext4fs_write_file(struct ext2_inode *file_inode,
-			     int pos, unsigned int len, char *buf)
+			     int pos, unsigned int len, const char *buf)
 {
 	int i;
 	int blockcnt;
@@ -764,7 +764,7 @@
 	int delayed_start = 0;
 	int delayed_extent = 0;
 	int delayed_next = 0;
-	char *delayed_buf = NULL;
+	const char *delayed_buf = NULL;
 
 	/* Adjust len so it we can't read past the end of the file. */
 	if (len > filesize)
@@ -816,7 +816,6 @@
 					 (uint32_t) delayed_extent);
 				previous_block_number = -1;
 			}
-			memset(buf, 0, fs->blksz - skipfirst);
 		}
 		buf += fs->blksz - skipfirst;
 	}
@@ -830,8 +829,8 @@
 	return len;
 }
 
-int ext4fs_write(const char *fname, unsigned char *buffer,
-					unsigned long sizebytes)
+int ext4fs_write(const char *fname, const char *buffer,
+		 unsigned long sizebytes)
 {
 	int ret = 0;
 	struct ext2_inode *file_inode = NULL;
@@ -949,7 +948,7 @@
 	if (ext4fs_put_metadata(temp_ptr, itable_blkno))
 		goto fail;
 	/* copy the file content into data blocks */
-	if (ext4fs_write_file(file_inode, 0, sizebytes, (char *)buffer) == -1) {
+	if (ext4fs_write_file(file_inode, 0, sizebytes, buffer) == -1) {
 		printf("Error in copying content\n");
 		/* FIXME: Deallocate data blocks */
 		goto fail;
diff --git a/include/ext4fs.h b/include/ext4fs.h
index 4b5de6e..7d48b2b 100644
--- a/include/ext4fs.h
+++ b/include/ext4fs.h
@@ -134,7 +134,7 @@
 int ext4fs_init(void);
 void ext4fs_deinit(void);
 int ext4fs_filename_unlink(char *filename);
-int ext4fs_write(const char *fname, unsigned char *buffer,
+int ext4fs_write(const char *fname, const char *buffer,
 		 unsigned long sizebytes);
 int ext4_write_file(const char *filename, void *buf, loff_t offset, loff_t len,
 		    loff_t *actwrite);