diff --git a/frontend/src/i18n/lang/ja-JP.json b/frontend/src/i18n/lang/ja-JP.json
index 4c53f30ee..2452373c0 100644
--- a/frontend/src/i18n/lang/ja-JP.json
+++ b/frontend/src/i18n/lang/ja-JP.json
@@ -181,6 +181,9 @@
 					"dark": "ダーク"
 				}
 			},
+			"backgroundBrightness": {
+				"title": "背景の明るさ"
+			},
 			"apiTokens": {
 				"title": "APIトークン",
 				"general": "APIトークンを使うとログインせずにVikunjaのAPIを利用できます。",