diff --git a/beacon_node/beacon_chain/src/observed_attestations.rs b/beacon_node/beacon_chain/src/observed_attestations.rs
index a9896f137..f74dd39ae 100644
--- a/beacon_node/beacon_chain/src/observed_attestations.rs
+++ b/beacon_node/beacon_chain/src/observed_attestations.rs
@@ -242,6 +242,7 @@ impl<E: EthSpec> ObservedAttestations<E> {
 }
 
 #[cfg(test)]
+#[cfg(not(debug_assertions))]
 mod tests {
     use super::*;
     use tree_hash::TreeHash;