diff --git a/public/script.js b/public/script.js
index dab17418d..f809c2dcd 100644
--- a/public/script.js
+++ b/public/script.js
@@ -1615,10 +1615,10 @@ async function Generate(type, { automatic_trigger, force_name2, resolve, reject,
 
     // Set empty promise resolution functions
     if (typeof resolve !== 'function') {
-        resolve = () => {};
+        resolve = () => { };
     }
     if (typeof reject !== 'function') {
-        reject = () => {};
+        reject = () => { };
     }
 
     if (selected_group && !is_group_generating) {
@@ -4080,7 +4080,7 @@ function isHordeGenerationNotAllowed() {
 }
 
 export function cancelTtsPlay() {
-    if (speechSynthesis) {
+    if ('speechSynthesis' in window) {
         speechSynthesis.cancel();
     }
 }
diff --git a/public/scripts/extensions/tts/system.js b/public/scripts/extensions/tts/system.js
index e07a32843..57d322a63 100644
--- a/public/scripts/extensions/tts/system.js
+++ b/public/scripts/extensions/tts/system.js
@@ -29,7 +29,7 @@ class SystemTtsProvider {
     }
 
     get settingsHtml() {
-        if (!window.speechSynthesis) {
+        if (!('speechSynthesis' in window)) {
             return "Your browser or operating system doesn't support speech synthesis";
         }
 
@@ -80,7 +80,7 @@ class SystemTtsProvider {
     //  TTS Interfaces //
     //#################//
     fetchTtsVoiceIds() {
-        if (!window.speechSynthesis) {
+        if (!('speechSynthesis' in window)) {
             return [];
         }
 
@@ -91,6 +91,10 @@ class SystemTtsProvider {
     }
 
     previewTtsVoice(voiceId) {
+        if (!('speechSynthesis' in window)) {
+            throw 'Speech synthesis API is not supported';
+        }
+
         const voice = speechSynthesis.getVoices().find(x => x.voiceURI === voiceId);
 
         if (!voice) {
@@ -107,11 +111,11 @@ class SystemTtsProvider {
     }
 
     async getVoice(voiceName) {
-        if (!window.speechSynthesis) {
+        if (!('speechSynthesis' in window)) {
             return { voice_id: null }
         }
 
-        const voices = window.speechSynthesis.getVoices();
+        const voices = speechSynthesis.getVoices();
         const match = voices.find(x => x.name == voiceName);
 
         if (!match) {
@@ -122,7 +126,7 @@ class SystemTtsProvider {
     }
 
     async generateTts(text, voiceId) {
-        if (!window.speechSynthesis) {
+        if (!('speechSynthesis' in window)) {
             throw 'Speech synthesis API is not supported';
         }