diff --git a/program/lib/Roundcube/rcube_mime.php b/program/lib/Roundcube/rcube_mime.php
index 2f24a1bb3..d21e3b4d5 100644
--- a/program/lib/Roundcube/rcube_mime.php
+++ b/program/lib/Roundcube/rcube_mime.php
@@ -595,11 +595,12 @@ class rcube_mime
             while (count($list)) {
                 $line   = array_shift($list);
                 $l      = mb_strlen($line);
-                $newlen = $len + $l + ($len ? 1 : 0);
+                $space  = $len ? 1 : 0;
+                $newlen = $len + $l + $space;
 
                 if ($newlen <= $width) {
-                    $string .= ($len ? ' ' : '').$line;
-                    $len += (1 + $l);
+                    $string .= ($space ? ' ' : '').$line;
+                    $len += ($space + $l);
                 }
                 else {
                     if ($l > $width) {
diff --git a/tests/src/format-flowed.txt b/tests/src/format-flowed.txt
index a390ffd11..359a41aec 100644
--- a/tests/src/format-flowed.txt
+++ b/tests/src/format-flowed.txt
@@ -1,7 +1,7 @@
 I'm replying on this with a very long line which is then wrapped and 
 space-stuffed because the draft is saved as format=flowed.
- From what's specified in RFC 2646 some lines need to be space-stuffed to 
-avoid muning during transport.
+ From what's specified in RFC 2646 some lines need to be space-stuffed to avoid 
+muning during transport.
 
 X