diff --git a/beacon_chain/utils/slot_clock/src/lib.rs b/beacon_chain/utils/slot_clock/src/lib.rs
index 7bdb775afe..4863f76698 100644
--- a/beacon_chain/utils/slot_clock/src/lib.rs
+++ b/beacon_chain/utils/slot_clock/src/lib.rs
@@ -4,7 +4,7 @@ mod testing_slot_clock;
 pub use crate::system_time_slot_clock::{Error as SystemTimeSlotClockError, SystemTimeSlotClock};
 pub use crate::testing_slot_clock::{Error as TestingSlotClockError, TestingSlotClock};
 
-pub trait SlotClock {
+pub trait SlotClock: Send + Sync {
     type Error;
 
     fn present_slot(&self) -> Result<Option<u64>, Self::Error>;