diff --git a/packages/sirv/index.mjs b/packages/sirv/index.mjs
index 3ad14d4..22eae25 100644
--- a/packages/sirv/index.mjs
+++ b/packages/sirv/index.mjs
@@ -101,7 +101,13 @@ function toHeaders(name, stats, isEtag) {
 	let enc = ENCODING[name.slice(-3)];
 
 	let ctype = lookup(name.slice(0, enc && -3)) || '';
-	if (ctype === 'text/html') ctype += ';charset=utf-8';
+	if (
+		ctype === 'application/json' ||
+		ctype === 'application/manifest+json' ||
+		ctype.startsWith('text/')
+	) {
+		ctype += ';charset=utf-8';
+	}
 
 	let headers = {
 		'Content-Length': stats.size,