diff --git a/acvm/src/lib.rs b/acvm/src/lib.rs
index 446fcd642..ea7388ac8 100644
--- a/acvm/src/lib.rs
+++ b/acvm/src/lib.rs
@@ -38,6 +38,7 @@ pub trait Backend:
     + CommonReferenceString
     + Default
     + Debug
+    + Sync
 {
 }