diff --git a/libisoburn/data_source.c b/libisoburn/data_source.c
index 540385fb..b31ec54f 100644
--- a/libisoburn/data_source.c
+++ b/libisoburn/data_source.c
@@ -76,7 +76,11 @@ int ds_read_block(IsoDataSource *src, uint32_t lba, uint8_t *buffer)
  struct isoburn_cached_drive *icd;
 
  if(src == NULL || buffer == NULL)
-   return -1;
+   /* It is not required by the specs of libisofs but implicitely assumed
+      by its current implementation that a data source read result <0 is
+      a valid libisofs error code.
+   */
+   return ISO_NULL_POINTER;
 
  icd = (struct isoburn_cached_drive *) src->data;
  d = (struct burn_drive*) icd->drive;
@@ -130,7 +134,10 @@ int ds_read_block(IsoDataSource *src, uint32_t lba, uint8_t *buffer)
    tiles[oldest].last_error_lba = lba;
    sprintf(msg, "ds_read_block(%lu) returns -1", (unsigned long) lba);
    burn_msgs_submit(0x00060000, msg, 0, "DEBUG", NULL);
-   return -1;
+
+   /* It is not required by the specs of libisofs but implicitely assumed ...
+   */
+   return ((int) ISO_FILE_READ_ERROR); 
  }
 
 #ifdef Libisoburn_read_cache_reporT
diff --git a/xorriso/xorriso_timestamp.h b/xorriso/xorriso_timestamp.h
index a231a62a..8a4c43ab 100644
--- a/xorriso/xorriso_timestamp.h
+++ b/xorriso/xorriso_timestamp.h
@@ -1 +1 @@
-#define Xorriso_timestamP "2008.05.01.124248"
+#define Xorriso_timestamP "2008.05.01.135421"