diff --git a/src/build/i18n.ts b/src/build/i18n.ts
index 1fb43a13c..57d6a20fd 100644
--- a/src/build/i18n.ts
+++ b/src/build/i18n.ts
@@ -55,8 +55,7 @@ export default class Replacer {
 
 	public replacement(ctx, match, a, b, c) {
 		const client = 'misskey/src/client/app/';
-		const name = ctx.src.substr(ctx.src.indexOf(client) + client.length);
-		if (name == '') return match;
+		const name = ctx ? ctx.src.substr(ctx.src.indexOf(client) + client.length) : null;
 
 		let key = a || b || c;
 		if (key[0] == '@') {
diff --git a/src/client/docs/api/gulpfile.ts b/src/client/docs/api/gulpfile.ts
index 9980ede23..31027c0be 100644
--- a/src/client/docs/api/gulpfile.ts
+++ b/src/client/docs/api/gulpfile.ts
@@ -127,7 +127,7 @@ gulp.task('doc:api:endpoints', async () => {
 						return;
 					}
 					const i18n = new I18nReplacer(lang);
-					html = html.replace(i18n.pattern, i18n.replacement);
+					html = html.replace(i18n.pattern, i18n.replacement.bind(null, null));
 					html = fa(html);
 					const htmlPath = `./built/client/docs/${lang}/api/endpoints/${ep.endpoint}.html`;
 					mkdirp(path.dirname(htmlPath), (mkdirErr) => {
@@ -171,7 +171,7 @@ gulp.task('doc:api:entities', async () => {
 						return;
 					}
 					const i18n = new I18nReplacer(lang);
-					html = html.replace(i18n.pattern, i18n.replacement);
+					html = html.replace(i18n.pattern, i18n.replacement.bind(null, null));
 					html = fa(html);
 					const htmlPath = `./built/client/docs/${lang}/api/entities/${kebab(entity.name)}.html`;
 					mkdirp(path.dirname(htmlPath), (mkdirErr) => {
diff --git a/src/client/docs/gulpfile.ts b/src/client/docs/gulpfile.ts
index 56bf6188c..5e81d6d3b 100644
--- a/src/client/docs/gulpfile.ts
+++ b/src/client/docs/gulpfile.ts
@@ -53,7 +53,7 @@ gulp.task('doc:docs', async () => {
 						return;
 					}
 					const i18n = new I18nReplacer(lang);
-					html = html.replace(i18n.pattern, i18n.replacement);
+					html = html.replace(i18n.pattern, i18n.replacement.bind(null, null));
 					html = fa(html);
 					const htmlPath = `./built/client/docs/${lang}/${name}.html`;
 					mkdirp(path.dirname(htmlPath), (mkdirErr) => {