---
 Cargo.toml | 1 +
 1 file changed, 1 insertion(+)

diff --git b/Cargo.toml a/Cargo.toml
index 1f5472d0..ca63f5b5 100644
--- b/Cargo.toml
+++ a/Cargo.toml
@@ -46,6 +46,7 @@ version = "1.8.0"
 optional = true
 
 [dev-dependencies]
+futures = "0.3.21"
 
 [features]
 default = ["std"]