diff --git a/src/rust/src/es/userdata.rs b/src/rust/src/es/userdata.rs
index 1e2534ccc..920809206 100644
--- a/src/rust/src/es/userdata.rs
+++ b/src/rust/src/es/userdata.rs
@@ -529,7 +529,6 @@ pub unsafe fn user_data(
     }
     // GXF vbi OEM code
     else if ud_header.starts_with(&[0x73, 0x52, 0x21, 0x06]) {
-        let udatalen = ustream.data.len() - ustream.pos;
         ustream.read_bytes(4)?; // skip header code
         ustream.read_bytes(2)?; // skip data length
         let line_nb = ustream.read_bits(16)? as u16;
@@ -544,7 +543,7 @@ pub unsafe fn user_data(
             info!("MPEG:VBI: only support Luma line");
         }
 
-        if udatalen < 720 {
+        if ustream.bits_left < 720 * 8 {
             info!("MPEG:VBI: Minimum 720 bytes in luma line required");
             return Ok(1);
         }