diff --git a/crates/composable-cow/src/poll.rs b/crates/composable-cow/src/poll.rs
index 590549cc..f68eb5c7 100644
--- a/crates/composable-cow/src/poll.rs
+++ b/crates/composable-cow/src/poll.rs
@@ -71,9 +71,9 @@ pub enum Verdict {
         /// orderbook prepends `from` before settlement).
         signature: Bytes,
         /// Advisory Unix timestamp (seconds) the fork's generator hints
-        /// the next poll at. `0` when synthetic - the legacy adapter
-        /// has no such hint, so the submit path ignores it.
-        next_poll_timestamp: u64,
+        /// the next poll at. `None` when synthetic - the legacy adapter
+        /// has no such hint.
+        next_poll_timestamp: Option<u64>,
     },
     /// Retry once the wall clock (Unix seconds, UTC) reaches
     /// `wait_until`.
diff --git a/crates/composable-cow/tests/run.rs b/crates/composable-cow/tests/run.rs
index b4b7e411..7466a7cd 100644
--- a/crates/composable-cow/tests/run.rs
+++ b/crates/composable-cow/tests/run.rs
@@ -134,7 +134,7 @@ fn ready_outcome(order: &GPv2OrderData) -> Verdict {
     Verdict::Post {
         order: Box::new(order.clone()),
         signature: hex!("c0ffeec0ffeec0ffee").to_vec().into(),
-        next_poll_timestamp: 0,
+        next_poll_timestamp: None,
     }
 }
 
diff --git a/modules/twap-monitor/src/keeper.rs b/modules/twap-monitor/src/keeper.rs
index e7719e8a..8168858f 100644
--- a/modules/twap-monitor/src/keeper.rs
+++ b/modules/twap-monitor/src/keeper.rs
@@ -327,14 +327,13 @@ fn poll_one<H: ChainHost>(
 /// `Post { order, signature, .. }`. The wire format is the canonical
 /// Solidity return tuple `abi.encode(order, signature)`, so the
 /// two-tuple parameter decode lines up. The deployed 1.x contract
-/// carries no next-poll hint, so `next_poll_timestamp` is synthetic
-/// (`0`).
+/// carries no next-poll hint, so `next_poll_timestamp` is `None`.
 fn decode_return(data: &[u8]) -> Option<Verdict> {
     let (order, signature) = <(GPv2OrderData, Bytes)>::abi_decode_params(data).ok()?;
     Some(Verdict::Post {
         order: Box::new(order),
         signature,
-        next_poll_timestamp: 0,
+        next_poll_timestamp: None,
     })
 }
 
@@ -569,7 +568,7 @@ mod tests {
                 assert_eq!(o.sellToken, order.sellToken);
                 assert_eq!(o.buyAmount, order.buyAmount);
                 assert_eq!(s, sig);
-                assert_eq!(next_poll_timestamp, 0, "legacy path carries no hint");
+                assert_eq!(next_poll_timestamp, None, "legacy path carries no hint");
             }
             other => panic!("expected Post, got {other:?}"),
         }