diff --git a/libemile/emile_first_set_param_scsi_extents.c b/libemile/emile_first_set_param_scsi_extents.c
index f19e6f5..9efbb47 100644
--- a/libemile/emile_first_set_param_scsi_extents.c
+++ b/libemile/emile_first_set_param_scsi_extents.c
@@ -15,10 +15,7 @@ static __attribute__((used)) char* rcsid = "$CVSHeader$";
 #include "libemile.h"
 #include "emile.h"
 
-#define BLOCK_SIZE	512	/* FIXME: should ask the disk driver */
-
-
-int emile_first_set_param_scsi_extents( int fd, int drive_num, int second_offset, int size)
+int emile_first_set_param_scsi_extents( int fd, int drive_num, int second_offset, int size, int blocksize)
 {
 	int ret;
 	char first[1024];
@@ -36,14 +33,14 @@ int emile_first_set_param_scsi_extents( int fd, int drive_num, int second_offset
 
 	max_blocks = read_short((u_int16_t*)&first[1022]) / 6;
 
-	write_short((u_int16_t*)&first[1014], BLOCK_SIZE);
+	write_short((u_int16_t*)&first[1014], blocksize);
 	write_short((u_int16_t*)&first[1016], drive_num);
 
 	write_long((u_int32_t*)&first[1018], 0);
 	current = 1014;
 
 	current -= 2;
-	write_short((u_int16_t*)&first[current], (size + BLOCK_SIZE - 1) / BLOCK_SIZE);
+	write_short((u_int16_t*)&first[current], (size + blocksize - 1) / blocksize);
 	current -= 4;
 	write_long((u_int32_t*)&first[current], second_offset);
 
@@ -51,7 +48,7 @@ int emile_first_set_param_scsi_extents( int fd, int drive_num, int second_offset
 	current -= 2;
 	write_short((u_int16_t*)(&first[current]), 0);
 	/* set second level size */
-	write_long((u_int32_t*)&first[1018], (size + BLOCK_SIZE - 1) / BLOCK_SIZE * BLOCK_SIZE);
+	write_long((u_int32_t*)&first[1018], (size + blocksize - 1) / blocksize * blocksize);
 	
 	ret = lseek(fd, location, SEEK_SET);
 	if (ret != location)
diff --git a/libemile/libemile.h b/libemile/libemile.h
index 358ac6f..9a9ef02 100644
--- a/libemile/libemile.h
+++ b/libemile/libemile.h
@@ -80,7 +80,8 @@ extern int emile_first_get_param(int fd, int *drive_num, int *second_offset,
 extern int emile_first_set_param_scsi(int fd, char *second_name);
 extern int emile_first_set_param_scsi_extents(int fd,
 				 int drive_num, int second_offset, 
-				 int second_size);
+				 int second_size,
+				 int blocksize);
 struct emile_container *emile_second_create_mapfile(short *unit_id, char *mapfile, char* kernel);
 extern int emile_is_url(char *path);
 extern int emile_floppy_create_image(char* first_level, char* second_level, 
diff --git a/tools/emile-first-tune.c b/tools/emile-first-tune.c
index 2358fd1..f348898 100644
--- a/tools/emile-first-tune.c
+++ b/tools/emile-first-tune.c
@@ -120,7 +120,8 @@ int first_tune_scsi( char* image, int drive_num, int second_offset, int size)
 	}
 
 	ret = emile_first_set_param_scsi_extents(fd, drive_num, 
-						 second_offset, size);
+						 second_offset, 
+						 size, BLOCK_SIZE);
 
 	close(fd);
 
diff --git a/tools/emile-mkisofs.c b/tools/emile-mkisofs.c
index 932fb9c..a9bcf93 100644
--- a/tools/emile-mkisofs.c
+++ b/tools/emile-mkisofs.c
@@ -271,7 +271,7 @@ static int set_first(char *image, int drive_num, int second_offset, int second_s
 
 	fd = open(image, O_RDWR);
 	ret = lseek(fd, start * 512, SEEK_SET);
-	ret = emile_first_set_param_scsi_extents(fd, 3, second_offset / 4, second_size);
+	ret = emile_first_set_param_scsi_extents(fd, 3, second_offset / 4, second_size, BLOCKSIZE);
 	close(fd);
 
 	return ret;