diff --git a/lib/tts-providers/mac-os.js b/lib/tts-providers/mac-os.js
index 53e82686..17e889ff 100644
--- a/lib/tts-providers/mac-os.js
+++ b/lib/tts-providers/mac-os.js
@@ -13,9 +13,9 @@ function macSay(phrase, voice) {
     return Promise.resolve();
   }
 
-  var selcetedRate = settings.macSay.rate;
-  if( !selcetedRate ) {
-    selcetedRate = "default";
+  var selectedRate = settings.macSay.rate;
+  if( !selectedRate ) {
+    selectedRate = "default";
   }
   var selectedVoice = settings.macSay.voice;
   if( voice ) {
@@ -24,7 +24,7 @@ function macSay(phrase, voice) {
 
   // Construct a filesystem neutral filename
   const phraseHash = crypto.createHash('sha1').update(phrase).digest('hex');
-  const filename = `macSay-${phraseHash}-${selcetedRate}-${selectedVoice}.m4a`;
+  const filename = `macSay-${phraseHash}-${selectedRate}-${selectedVoice}.m4a`;
   const filepath = path.resolve(settings.webroot, 'tts', filename);
 
   const expectedUri = `/tts/${filename}`;
@@ -52,13 +52,13 @@ function macSay(phrase, voice) {
     // System Preferences -> Accessibility -> Speech -> System Voice
     //
 
-    var execCommand = `say "${phrase}" -o ${filepath}`;
-    if( selectedVoice && selcetedRate != "default" ) {
-      execCommand = `say -r ${selcetedRate} -v ${selectedVoice} "${phrase}" -o ${filepath}`;
+    var execCommand = `say "${phrase}" -o ${filepath} --data-format=aac`;
+    if( selectedVoice && selectedRate != "default" ) {
+      execCommand = `say -r ${selectedRate} -v ${selectedVoice} "${phrase}" -o ${filepath} --data-format=aac`;
     } else if ( selectedVoice ) {
-      execCommand = `say -v ${selectedVoice} "${phrase}" -o ${filepath}`;
-    } else if ( selcetedRate  != "default" ) {
-      execCommand = `say -r ${selcetedRate} "${phrase}" -o ${filepath}`;
+      execCommand = `say -v ${selectedVoice} "${phrase}" -o ${filepath} --data-format=aac`;
+    } else if ( selectedRate  != "default" ) {
+      execCommand = `say -r ${selectedRate} "${phrase}" -o ${filepath} --data-format=aac`;
     }
 
     exec(execCommand,