diff --git a/src/mime/type.go b/src/mime/type.go
index ad763133e6..aa05077e22 100644
--- a/src/mime/type.go
+++ b/src/mime/type.go
@@ -63,8 +63,8 @@ var builtinTypesLower = map[string]string{
 	".html": "text/html; charset=utf-8",
 	".jpeg": "image/jpeg",
 	".jpg":  "image/jpeg",
-	".js":   "application/javascript",
-	".mjs":  "application/javascript",
+	".js":   "text/javascript; charset=utf-8",
+	".mjs":  "text/javascript; charset=utf-8",
 	".pdf":  "application/pdf",
 	".png":  "image/png",
 	".svg":  "image/svg+xml",