diff --git a/xorriso/write_run.c b/xorriso/write_run.c
index 5947558e..6f003343 100644
--- a/xorriso/write_run.c
+++ b/xorriso/write_run.c
@@ -864,6 +864,7 @@ int Xorriso_make_iso_write_opts(struct XorrisO *xorriso, IsoImage *image,
                                 struct isoburn_imgen_opts *sopts, int flag)
 {
  int ext, i, ret, pad_by_libisofs= 0, is_bootable= 0, relax, intvl_string= 0;
+ int intvl_check= 2; /* 3 forbids "imported_iso" */
  char *out_cs, *part_image;
  IsoNode *root_node;
  uint32_t padding;
@@ -926,7 +927,7 @@ int Xorriso_make_iso_write_opts(struct XorrisO *xorriso, IsoImage *image,
                                  xorriso->scdbackup_tag_written);
  if(xorriso->prep_partition[0]) {
    part_image= xorriso->prep_partition;
-   intvl_string= Xorriso_check_intvl_string(xorriso, &part_image, 3);
+   intvl_string= Xorriso_check_intvl_string(xorriso, &part_image, intvl_check);
    if(intvl_string < 0)
      {ret= 0; goto ex;}
    ret= isoburn_igopt_set_prep_partition(sopts, part_image, intvl_string);
@@ -935,7 +936,7 @@ int Xorriso_make_iso_write_opts(struct XorrisO *xorriso, IsoImage *image,
  }
  if(xorriso->efi_boot_partition[0]) {
    part_image= xorriso->efi_boot_partition;
-   intvl_string= Xorriso_check_intvl_string(xorriso, &part_image, 3);
+   intvl_string= Xorriso_check_intvl_string(xorriso, &part_image, intvl_check);
    if(intvl_string < 0)
      {ret= 0; goto ex;}
    ret= isoburn_igopt_set_efi_bootp(sopts, part_image, intvl_string);
@@ -951,7 +952,7 @@ int Xorriso_make_iso_write_opts(struct XorrisO *xorriso, IsoImage *image,
      part_image= "";
    else
      part_image= xorriso->appended_partitions[i];
-   intvl_string= Xorriso_check_intvl_string(xorriso, &part_image, 3);
+   intvl_string= Xorriso_check_intvl_string(xorriso, &part_image, intvl_check);
    if(intvl_string < 0)
      {ret= 0; goto ex;}
    isoburn_igopt_set_partition_img(sopts, i + 1,
diff --git a/xorriso/xorriso_timestamp.h b/xorriso/xorriso_timestamp.h
index eb365081..3476d871 100644
--- a/xorriso/xorriso_timestamp.h
+++ b/xorriso/xorriso_timestamp.h
@@ -1 +1 @@
-#define Xorriso_timestamP "2017.08.24.102256"
+#define Xorriso_timestamP "2017.08.24.102427"