"mt tell" says no such device with kernel-2.6.9-5.0.5.EL.
Patch below:

--- st.c 2005-04-13 10:45:00.240790000 +0100
+++ st.c.new 2005-04-13 13:44:41.356696328 +0100
@@ -3126,8 +3126,9 @@
* access to the device is prohibited.
*/
retval = scsi_nonblockable_ioctl(STp->device, cmd_in, p, file);
- if (!scsi_block_when_processing_errors(STp->device) || !retval)
+ if (!scsi_block_when_processing_errors(STp->device) || retval != -ENODEV)
goto out;
+ retval = 0;
 
cmd_type = _IOC_TYPE(cmd_in);
cmd_nr = _IOC_NR(cmd_in);