diff --git a/src/derive/stages/batcher_transactions.rs b/src/derive/stages/batcher_transactions.rs
index 51345fb3..ccd72809 100644
--- a/src/derive/stages/batcher_transactions.rs
+++ b/src/derive/stages/batcher_transactions.rs
@@ -108,7 +108,11 @@ impl Frame {
 
         let frame_data = data[22..frame_data_end].to_vec();
 
-        let is_last = data[frame_data_end] != 0;
+        let is_last = if data[frame_data_end] > 1 {
+            eyre::bail!("invalid is_last flag");
+        } else {
+            data[frame_data_end] != 0
+        };
 
         let frame = Self {
             channel_id,