diff --git a/src/client/server_info.rs b/src/client/server_info.rs
index 15bb618..5090146 100644
--- a/src/client/server_info.rs
+++ b/src/client/server_info.rs
@@ -48,7 +48,7 @@ impl ServerInfo {
         match self.esmtp_features {
             Some(ref esmtp_features) => {
                 for feature in esmtp_features.iter() {
-                    if keyword.same_extension_as(*feature) {
+                    if keyword.same_extension_as(feature) {
                         return Some(*feature);
                     }
                 }
diff --git a/src/extension.rs b/src/extension.rs
index 67c4cd8..3fd2a5b 100644
--- a/src/extension.rs
+++ b/src/extension.rs
@@ -19,7 +19,7 @@ use response::Response;
 use self::Extension::{EightBitMime, SmtpUtfEight, StartTls, Size};
 
 /// Supported ESMTP keywords
-#[deriving(PartialEq,Eq,Clone)]
+#[deriving(PartialEq,Eq,Copy,Clone)]
 pub enum Extension {
     /// 8BITMIME keyword
     ///
@@ -74,12 +74,12 @@ impl FromStr for Extension {
 
 impl Extension {
     /// Checks if the ESMTP keyword is the same
-    pub fn same_extension_as(&self, other: Extension) -> bool {
-        if *self == other {
+    pub fn same_extension_as(&self, other: &Extension) -> bool {
+        if self == other {
             return true;
         }
-        match (*self, other) {
-            (Size(_), Size(_)) => true,
+        match (self, other) {
+            (&Size(_), &Size(_)) => true,
             _ => false,
         }
     }
@@ -128,10 +128,11 @@ mod test {
 
     #[test]
     fn test_same_extension_as() {
-        assert_eq!(Extension::EightBitMime.same_extension_as(Extension::EightBitMime), true);
-        assert_eq!(Extension::Size(42).same_extension_as(Extension::Size(42)), true);
-        assert_eq!(Extension::Size(42).same_extension_as(Extension::Size(43)), true);
-        assert_eq!(Extension::Size(42).same_extension_as(Extension::EightBitMime), false);
+        assert_eq!(Extension::EightBitMime.same_extension_as(&Extension::EightBitMime), true);
+        assert_eq!(Extension::Size(42).same_extension_as(&Extension::Size(42)), true);
+        assert_eq!(Extension::Size(42).same_extension_as(&Extension::Size(43)), true);
+        assert_eq!(Extension::Size(42).same_extension_as(&Extension::EightBitMime), false);
+        assert_eq!(Extension::EightBitMime.same_extension_as(&Extension::SmtpUtfEight), false);
     }
 
     #[test]
diff --git a/src/transaction.rs b/src/transaction.rs
index ccfb907..dcd9b04 100644
--- a/src/transaction.rs
+++ b/src/transaction.rs
@@ -18,7 +18,7 @@ use command::Command;
 use self::TransactionState::{Unconnected, Connected, HelloSent, MailSent, RecipientSent, DataSent};
 
 /// Contains the state of the current transaction
-#[deriving(PartialEq,Eq,Clone)]
+#[deriving(PartialEq,Eq,Copy)]
 pub enum TransactionState {
     /// No connection was established
     Unconnected,