diff --git a/src/vdaf/prio3.rs b/src/vdaf/prio3.rs
index 8989925ed..6878a61e8 100644
--- a/src/vdaf/prio3.rs
+++ b/src/vdaf/prio3.rs
@@ -842,6 +842,7 @@ where
 }
 
 /// State of each [`Aggregator`] during the Preparation phase.
+#[derive(Clone, Eq, PartialEq)]
 pub struct Prio3PrepareState<F, const SEED_SIZE: usize> {
     measurement_share: Share<F, SEED_SIZE>,
     joint_rand_seed: Option<Seed<SEED_SIZE>>,