diff --git a/src/tape/drive/mam.rs b/src/tape/drive/mam.rs
index 4fa16c3f..54b8100e 100644
--- a/src/tape/drive/mam.rs
+++ b/src/tape/drive/mam.rs
@@ -101,12 +101,13 @@ lazy_static::lazy_static!{
 
 fn read_tape_mam<F: AsRawFd>(file: &mut F) -> Result<Vec<u8>, Error> {
 
-    let mut sg_raw = SgRaw::new(file, 32*1024)?;
+    let alloc_len: u32 = 32*1024;
+    let mut sg_raw = SgRaw::new(file, alloc_len as usize)?;
 
     let mut cmd = Vec::new();
     cmd.extend(&[0x8c, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8]);
     cmd.extend(&[0u8, 0u8]); // first attribute
-    cmd.extend(&[0u8, 0u8, 0x8f, 0xff]); // alloc len
+    cmd.extend(&alloc_len.to_be_bytes()); // alloc len
     cmd.extend(&[0u8, 0u8]);
 
     sg_raw.do_command(&cmd)