diff --git a/ed25519/Cargo.toml b/ed25519/Cargo.toml
index 74be60f5..55cc62ab 100644
--- a/ed25519/Cargo.toml
+++ b/ed25519/Cargo.toml
@@ -14,6 +14,7 @@ edition = "2018"
 readme = "README.md"
 categories = ["cryptography", "no-std"]
 keywords = ["crypto", "curve25519", "ecc", "signature", "signing"]
+rust-version = "1.56"
 
 [dependencies]
 signature = { version = ">=1.3.1", default-features = false }