diff --git a/consensus/types/src/sync_selection_proof.rs b/consensus/types/src/sync_selection_proof.rs
index e4f6ce43cd..61302a9dfb 100644
--- a/consensus/types/src/sync_selection_proof.rs
+++ b/consensus/types/src/sync_selection_proof.rs
@@ -13,6 +13,7 @@ use ssz_types::typenum::Unsigned;
 use std::cmp;
 
 #[derive(arbitrary::Arbitrary, PartialEq, Debug, Clone, Serialize, Deserialize)]
+#[serde(transparent)]
 pub struct SyncSelectionProof(Signature);
 
 impl SyncSelectionProof {