diff --git a/libisofs/ecma119.c b/libisofs/ecma119.c
index 9911345..cdee22a 100644
--- a/libisofs/ecma119.c
+++ b/libisofs/ecma119.c
@@ -1108,7 +1108,35 @@ int zero_writer_free_data(IsoImageWriter *writer)
 }
 
 static
-int zero_writer_create(Ecma119Image *target, uint32_t num_blocks)
+int tail_writer_compute_data_blocks(IsoImageWriter *writer)
+{
+    int ret;
+    Ecma119Image *target;
+    struct iso_zero_writer_data_struct *data;
+
+    target = writer->target;
+    ret = iso_align_isohybrid(target, 0);
+    if (ret < 0)
+        return ret;
+    data = (struct iso_zero_writer_data_struct *) writer->data;
+    if (data->num_blocks != target->tail_blocks) {
+        iso_msg_debug(target->image->id,
+                      "Aligned image size for isohybrid by %d blocks",
+                      target->tail_blocks - data->num_blocks);
+        data->num_blocks = target->tail_blocks;
+    }
+    if (target->tail_blocks <= 0)
+        return ISO_SUCCESS;
+    ret = zero_writer_compute_data_blocks(writer);
+    return ret;
+}
+
+/*
+  @param flag bit0= use tail_writer_compute_data_blocks rather than
+                    zero_writer_compute_data_blocks
+*/
+static
+int zero_writer_create(Ecma119Image *target, uint32_t num_blocks, int flag)
 {
     IsoImageWriter *writer;
     struct iso_zero_writer_data_struct *data;
@@ -1124,7 +1152,11 @@ int zero_writer_create(Ecma119Image *target, uint32_t num_blocks)
     }
     data->num_blocks = num_blocks;
 
-    writer->compute_data_blocks = zero_writer_compute_data_blocks;
+    if (flag & 1) {
+        writer->compute_data_blocks = tail_writer_compute_data_blocks;
+    } else {
+        writer->compute_data_blocks = zero_writer_compute_data_blocks;
+    }
     writer->write_vol_desc = zero_writer_write_vol_desc;
     writer->write_data = zero_writer_write_data;
     writer->free_data = zero_writer_free_data;
@@ -1695,9 +1727,9 @@ int ecma119_image_new(IsoImage *src, IsoWriteOpts *opts, Ecma119Image **img)
     target->partition_secs_per_head = opts->partition_secs_per_head;
     target->partition_heads_per_cyl = opts->partition_heads_per_cyl;
     if (target->partition_secs_per_head == 0)
-        target->partition_secs_per_head = 63;
+        target->partition_secs_per_head = 32;
     if (target->partition_heads_per_cyl == 0)
-        target->partition_heads_per_cyl = 255;
+        target->partition_heads_per_cyl = 64;
     target->eff_partition_offset = 0;
     target->partition_root = NULL;
     target->partition_l_table_pos = 0;
@@ -1893,11 +1925,9 @@ int ecma119_image_new(IsoImage *src, IsoWriteOpts *opts, Ecma119Image **img)
 
 
     /* IMPORTANT: This must be the last writer before the checksum writer */
-    if (target->tail_blocks > 0) {
-        ret = zero_writer_create(target, target->tail_blocks);
-        if (ret < 0)
-            goto target_cleanup;
-    }
+    ret = zero_writer_create(target, target->tail_blocks, 1);
+    if (ret < 0)
+        goto target_cleanup;
 
     if ((target->md5_file_checksums & 1) || target->md5_session_checksum) {
         ret = checksum_writer_create(target);
@@ -1951,8 +1981,8 @@ int ecma119_image_new(IsoImage *src, IsoWriteOpts *opts, Ecma119Image **img)
         if (i == el_torito_writer_index)
     continue;
 
-        /* Exposing address of data start to IsoWriteOpts iand memorizing
-           this address for for all files which have no block address: 
+        /* Exposing address of data start to IsoWriteOpts and memorizing
+           this address for all files which have no block address: 
            symbolic links, device files, empty data files.
            filesrc_writer_compute_data_blocks() and filesrc_writer_write_data()
            will account resp. write this single block. 
diff --git a/libisofs/libisofs.h b/libisofs/libisofs.h
index ca8e9e1..e0a1b73 100644
--- a/libisofs/libisofs.h
+++ b/libisofs/libisofs.h
@@ -3120,6 +3120,8 @@ int el_torito_seems_boot_info_table(ElToritoBootImage *bootimg, int flag);
  * Specifies options for ISOLINUX or GRUB boot images. This should only be used
  * if the type of boot image is known.
  *
+ * @param bootimg
+ *      The image to set options on 
  * @param options
  *        bitmask style flag. The following values are defined:
  *
@@ -3147,8 +3149,6 @@ int el_torito_seems_boot_info_table(ElToritoBootImage *bootimg, int flag);
  *                 For that you need isolinux.bin from SYSLINUX 3.72 or later.
  *                 IMPORTANT: The application has to take care that the image
  *                            on media gets padded up to the next full MB.
- * @param bootimg
- *      The image to set options on 
  * @param flag
  *        Reserved for future usage, set to 0.
  * @return
diff --git a/libisofs/make_isohybrid_mbr.c b/libisofs/make_isohybrid_mbr.c
index a26d809..e544fcc 100644
--- a/libisofs/make_isohybrid_mbr.c
+++ b/libisofs/make_isohybrid_mbr.c
@@ -386,21 +386,19 @@ int make_isolinux_mbr(int32_t *img_blocks, uint32_t boot_lba,
                       int part_offset, int part_number, int fs_type,
                       uint8_t *buf, int flag)
 {
-    uint32_t spc, id, part, nominal_part_size;
+    uint32_t id, part, nominal_part_size;
     off_t hd_img_blocks, hd_boot_lba;
     char *wpt;
     /* For generating a weak random number */
     struct timeval tv;
     struct timezone tz;
 
-    /* Pad image_size to a multiple of sector_count*head_count
-    */
-    spc = head_count * sector_count;
     hd_img_blocks = ((off_t) *img_blocks) * (off_t) 4;
-    if (hd_img_blocks % spc) {
-        hd_img_blocks += spc - (hd_img_blocks % spc);
-        *img_blocks = hd_img_blocks / 4 + !!(hd_img_blocks % 4);
-    }
+
+    /* Padding of image_size to a multiple of sector_count*head_count
+       happens already at compute time and is implemented by
+       an appropriate increase of Ecma119Image->tail_blocks.
+    */
 
     wpt = (char *) buf + 432;
 
diff --git a/libisofs/system_area.c b/libisofs/system_area.c
index ef02a7e..396abe7 100644
--- a/libisofs/system_area.c
+++ b/libisofs/system_area.c
@@ -809,3 +809,100 @@ int iso_write_system_area(Ecma119Image *t, uint8_t *buf)
 
     return ISO_SUCCESS;
 }
+
+/* Choose *heads_per_cyl so that
+   - *heads_per_cyl * secs_per_head * 1024 >= imgsize / 512
+   - *heads_per_cyl * secs_per_head is divisible by 4
+   - it is as small as possible (to reduce aligment overhead)
+   - it is <= 255
+   @return 1= success , 0= cannot achieve goals
+*/
+static
+int try_sph(off_t imgsize, int secs_per_head, int *heads_per_cyl, int flag)
+{
+    off_t hd_blocks, hpc;
+
+    hd_blocks= imgsize / 512;
+    hpc = hd_blocks / secs_per_head / 1024;
+    if (hpc * secs_per_head * 1024 < hd_blocks)
+        hpc++;
+    if ((secs_per_head % 4) == 0) {
+        ;
+    } else if ((secs_per_head % 2) == 0) {
+        hpc += (hpc % 2);
+    } else if(hpc % 4) {
+        hpc += 4 - (hpc % 4);
+    }
+    if (hpc > 255)
+        return 0;
+    *heads_per_cyl = hpc;
+    return 1;
+}
+
+int iso_align_isohybrid(Ecma119Image *t, int flag)
+{
+    int sa_type, ret;
+    uint32_t img_blocks;
+    off_t imgsize, cylsize = 0, frac;
+
+    sa_type = (t->system_area_options >> 2) & 0x3f;
+    if (sa_type != 0)
+        return ISO_SUCCESS;
+
+    img_blocks = t->curblock;
+    imgsize = ((off_t) img_blocks) * (off_t) 2048;
+    if ((t->system_area_options & 3)
+        && (off_t) (t->partition_heads_per_cyl * t->partition_secs_per_head
+                    * 1024) * (off_t) 512 < imgsize) {
+        /* Choose small values which can represent the image size */
+        /* First try 32 sectors per head */
+        ret = try_sph(imgsize, 32, &(t->partition_heads_per_cyl), 0);
+        if (ret == 1) {
+            t->partition_secs_per_head = 32;
+        } else {
+            /* Did not work with 32. Try 63 */
+            t->partition_secs_per_head = 63;
+            ret = try_sph(imgsize, 63, &(t->partition_heads_per_cyl), 0);
+            if (ret != 1)
+                t->partition_heads_per_cyl = 255;
+        }
+        cylsize = t->partition_heads_per_cyl * t->partition_secs_per_head *512;
+        frac = imgsize % cylsize;
+        iso_msg_debug(t->image->id,
+                      "Automatically adjusted MBR geometry to %d/%d/%d",
+                      (int) (imgsize / cylsize + !!frac),
+                      t->partition_heads_per_cyl, t->partition_secs_per_head);
+    }
+
+    cylsize = 0;
+    if (sa_type == 0 && t->catalog != NULL &&
+               (t->catalog->bootimages[0]->isolinux_options & 0x0a) == 0x02) {
+        /* Check for isolinux image with magic number of 3.72 and produce
+           an MBR from our built-in template. (Deprecated since 31 Mar 2010)
+        */
+        if (img_blocks >= 0x40000000)
+            return ISO_SUCCESS;
+        cylsize = 64 * 32 * 512;
+    } else if (sa_type == 0 && (t->system_area_options & 2)) {
+        /* Patch externally provided system area as isohybrid MBR */
+        if (t->catalog == NULL || t->system_area_data == NULL) {
+            /* isohybrid makes only sense together with ISOLINUX boot image
+               and externally provided System Area.
+            */
+            return ISO_ISOLINUX_CANT_PATCH;
+        }
+        cylsize = t->partition_heads_per_cyl * t->partition_secs_per_head
+                  * 512;
+    } 
+    if (cylsize == 0)
+        return ISO_SUCCESS;
+
+    frac = imgsize % cylsize;
+    imgsize += (frac > 0 ? cylsize - frac : 0);
+
+    frac = imgsize - ((off_t) img_blocks) * (off_t) 2048;
+    if (frac == 0)
+        return ISO_SUCCESS;
+    t->tail_blocks += frac / 2048 + !!(frac % 2048);
+    return ISO_SUCCESS;
+}
diff --git a/libisofs/system_area.h b/libisofs/system_area.h
index cdf1a2e..444f8b7 100644
--- a/libisofs/system_area.h
+++ b/libisofs/system_area.h
@@ -46,6 +46,11 @@ int make_isohybrid_mbr(int bin_lba, int *img_blocks, char *mbr, int flag);
  */
 int iso_write_system_area(Ecma119Image *t, uint8_t *buf);
 
+/**
+ * Adjust t->tail_blocks to the eventual alignment needs of isohybrid booting.
+ */
+int iso_align_isohybrid(Ecma119Image *t, int flag);
+
 
 /** 
  * Read the necessary ELF information from the first MIPS boot file.