diff --git a/Cargo.toml b/Cargo.toml
index 2247ec9..dd6c129 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -40,7 +40,7 @@ serde_json = { version = "1", optional = true }
 # smtp-transport
 nom = { version = "7", optional = true }
 hostname = { version = "0.3", optional = true } # feature
-socket2 = { version = "0.4.4", optional = true }
+socket2 = { version = "0.5.1", optional = true }
 
 ## tls
 native-tls = { version = "0.2", optional = true } # feature