diff --git a/ethers-contract/src/call.rs b/ethers-contract/src/call.rs
index 021965f14..424e9f2cf 100644
--- a/ethers-contract/src/call.rs
+++ b/ethers-contract/src/call.rs
@@ -255,7 +255,7 @@ where
 impl<B, M, D> IntoFuture for FunctionCall<B, M, D>
 where
     Self: 'static,
-    B: Borrow<M>,
+    B: Borrow<M> + Send + Sync,
     M: Middleware,
     D: Detokenize + Send + Sync,
 {