diff --git a/src/client/app/boot.js b/src/client/app/boot.js
index 6bcceec217..86d48faf1a 100644
--- a/src/client/app/boot.js
+++ b/src/client/app/boot.js
@@ -43,7 +43,7 @@
 	if (LANGS.includes(navigator.language)) {
 		lang = navigator.language;
 	} else {
-		lang = LANGS.find(x => x.split('-')[0] == lang);
+		lang = LANGS.find(x => x.split('-')[0] == navigator.language);
 
 		if (lang == null) {
 			// Fallback
diff --git a/src/misc/i18n.ts b/src/misc/i18n.ts
index a07af3e939..8379b2f538 100644
--- a/src/misc/i18n.ts
+++ b/src/misc/i18n.ts
@@ -30,7 +30,7 @@ export default class Replacer {
 			if (text.hasOwnProperty(path)) {
 				text = text[path];
 			} else {
-				if (this.lang === 'ja') console.warn(`path '${path}' not found`);
+				if (this.lang === 'ja-JP') console.warn(`path '${path}' not found`);
 				return key; // Fallback
 			}
 		}
@@ -46,10 +46,10 @@ export default class Replacer {
 		});
 
 		if (error) {
-			if (this.lang === 'ja') console.warn(`key '${key}' not found in '${path}'`);
+			if (this.lang === 'ja-JP') console.warn(`key '${key}' not found in '${path}'`);
 			return key; // Fallback
 		} else if (typeof text !== 'string') {
-			if (this.lang === 'ja') console.warn(`key '${key}' is not string in '${path}'`);
+			if (this.lang === 'ja-JP') console.warn(`key '${key}' is not string in '${path}'`);
 			return key; // Fallback
 		} else {
 			return text;