diff --git a/crates/flashtypes/src/block.rs b/crates/flashtypes/src/block.rs
index c6aec69a..701aa414 100644
--- a/crates/flashtypes/src/block.rs
+++ b/crates/flashtypes/src/block.rs
@@ -92,6 +92,27 @@ mod tests {
         assert_eq!(decoded.metadata.block_number, 1234);
     }
 
+    #[rstest]
+    #[case::plain(encode_plain)]
+    #[case::brotli(encode_brotli)]
+    fn try_decode_old_format_still_decodes(#[case] encoder: fn(&FlashblocksPayloadV1) -> Bytes) {
+        // old format should still decode
+        let payload = sample_payload(json!({
+            "block_number": 1234u64,
+            "receipts": {},
+            "new_account_balances": {},
+        }));
+
+        let decoded =
+            Flashblock::try_decode_message(encoder(&payload)).expect("payload should decode");
+
+        assert_eq!(decoded.payload_id, payload.payload_id);
+        assert_eq!(decoded.index, payload.index);
+        assert_eq!(decoded.base, payload.base);
+        assert_eq!(decoded.diff, payload.diff);
+        assert_eq!(decoded.metadata.block_number, 1234);
+    }
+
     #[rstest]
     #[case::invalid_brotli(Bytes::from_static(b"not brotli data"))]
     #[case::missing_metadata(encode_plain(&sample_payload(json!({