diff --git a/src/backends/appkit.rs b/src/backends/appkit.rs
index ec32729..164cf53 100644
--- a/src/backends/appkit.rs
+++ b/src/backends/appkit.rs
@@ -204,7 +204,7 @@ impl Backend for AppKit {
         unimplemented!()
     }
 
-    fn set_voice(&self, voice: String) -> Result<(),Error> {
+    fn set_voice(&mut self, voice: String) -> Result<(),Error> {
         unimplemented!()
     }
 }
diff --git a/src/backends/av_foundation.rs b/src/backends/av_foundation.rs
index 70e3f33..c51988a 100644
--- a/src/backends/av_foundation.rs
+++ b/src/backends/av_foundation.rs
@@ -29,7 +29,7 @@ impl AvFoundation {
                 rate: 0.5,
                 volume: 1.,
                 pitch: 1.,
-                voice: AVSpeechSynthesisVoice::new(),
+                voice: AVSpeechSynthesisVoice::default(),
             }
         }
     }
@@ -59,6 +59,7 @@ impl Backend for AvFoundation {
             let _: () = msg_send![utterance, setRate: self.rate];
             let _: () = msg_send![utterance, setVolume: self.volume];
             let _: () = msg_send![utterance, setPitchMultiplier: self.pitch];
+            let _: () = msg_send![utterance, setVoice: self.voice];
             let _: () = msg_send![self.synth, speakUtterance: utterance];
         }
         Ok(())
@@ -149,7 +150,8 @@ impl Backend for AvFoundation {
         AVSpeechSynthesisVoice::list().iter().map(|v| {v.identifier()}).collect()
     }
 
-    fn set_voice(&self, voice: String) -> Result<(),Error> {
+    fn set_voice(&mut self, voice: String) -> Result<(),Error> {
+        self.voice = AVSpeechSynthesisVoice::new(voice);
         Ok(())
     }
 }
diff --git a/src/backends/av_foundation/voices.rs b/src/backends/av_foundation/voices.rs
index 98c6036..a23c14a 100644
--- a/src/backends/av_foundation/voices.rs
+++ b/src/backends/av_foundation/voices.rs
@@ -8,8 +8,14 @@ use core_foundation::string::CFString;
 pub struct AVSpeechSynthesisVoice(*const Object);
 
 impl AVSpeechSynthesisVoice {
-    pub fn new() -> Self {
-        Self::list()[0]
+    pub fn new(identifier: String) -> Self {
+        let i: CFString = CFString::from(identifier.as_str());
+        let voice: *const Object = unsafe{msg_send![class!(AVSpeechSynthesisVoice).metaclass(), voiceWithIdentifier: i]};
+        AVSpeechSynthesisVoice{0: voice}
+    }
+
+    pub fn default() -> Self {
+        AVSpeechSynthesisVoice::list()[0]
     }
 
     pub fn list() -> Vec<Self> {
diff --git a/src/lib.rs b/src/lib.rs
index af6db3f..61a47ae 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -102,7 +102,7 @@ pub trait Backend {
     fn is_speaking(&self) -> Result<bool, Error>;
     fn voice(&self) -> Result<String, Error>;
     fn list_voices(&self) -> Vec<String>;
-    fn set_voice(&self, voice: String) -> Result<(),Error>;
+    fn set_voice(&mut self, voice: String) -> Result<(),Error>;
 }
 
 pub struct TTS(Box<dyn Backend>);
@@ -399,7 +399,7 @@ impl TTS {
     /**
      * Set speaking voice.
      */
-    pub fn set_voice(&self, voice: String) -> Result<(),Error> {
+    pub fn set_voice(&mut self, voice: String) -> Result<(),Error> {
         let Features {
             voices: voices_feature,
             ..