diff --git a/R/mime.R b/R/mime.R
index a9ffcabd..3c227345 100644
--- a/R/mime.R
+++ b/R/mime.R
@@ -511,7 +511,7 @@ header_unstructured <- function(
 
     if (encode_unicode) {
       str <- enc2utf8(str)
-      str <- sprintf("=?utf-8?B?%s?=", base64enc::base64encode(charToRaw(str)), 0)
+      str <- sprintf("=?utf-8?B?%s?=", base64enc::base64encode(charToRaw(str)))
 
     } else {