diff --git a/scst/src/dev_handlers/scst_tape.c b/scst/src/dev_handlers/scst_tape.c
index 7c0ffd344..9d0cc4a2c 100644
--- a/scst/src/dev_handlers/scst_tape.c
+++ b/scst/src/dev_handlers/scst_tape.c
@@ -145,7 +145,7 @@ static int tape_attach(struct scst_device *dev)
 	}
 
 	dev->block_size = TAPE_DEF_BLOCK_SIZE;
-	dev->block_shift = -1; /* not used */
+	dev->block_shift = scst_calc_block_shift(dev->block_size);
 
 	buffer = kmalloc(buffer_size, GFP_KERNEL);
 	if (!buffer) {
@@ -203,7 +203,7 @@ static int tape_attach(struct scst_device *dev)
 		res = -ENODEV;
 		goto out_free_buf;
 	}
-	dev->block_shift = -1; /* not used */
+	dev->block_shift = scst_calc_block_shift(dev->block_size);
 
 obtain:
 	res = scst_obtain_device_parameters(dev, NULL);
@@ -250,7 +250,7 @@ static void tape_set_block_size(struct scst_cmd *cmd, int block_size)
 	 * there are existing commands.
 	 */
 	dev->block_size = block_size;
-	dev->block_shift = -1; /* not used */
+	dev->block_shift = scst_calc_block_shift(dev->block_size);
 	return;
 }
 
diff --git a/scst/src/scst_lib.c b/scst/src/scst_lib.c
index 302f97e0a..c5a3c632f 100644
--- a/scst/src/scst_lib.c
+++ b/scst/src/scst_lib.c
@@ -12470,6 +12470,8 @@ int scst_tape_generic_parse(struct scst_cmd *cmd)
 				shift_left_overflows(cmd->data_len, block_shift) ||
 				shift_left_overflows(cmd->out_bufflen, block_shift);
 
+		EXTRACHECKS_BUG_ON(block_shift < 0);
+		
 		BUILD_BUG_ON(sizeof(cmd->bufflen) != 4);
 		BUILD_BUG_ON(sizeof(cmd->out_bufflen) != 4);
 		if (unlikely(overflow)) {