diff --git a/src/message.c b/src/message.c
index fe72e43..7aec2d6 100644
--- a/src/message.c
+++ b/src/message.c
@@ -298,9 +298,9 @@
 	{
 	    do
 		half = half - (*mb_head_off)(s, s + half - 1) - 1;
-	    while (utf_iscomposing(utf_ptr2char(s + half)) && half > 0);
+	    while (half > 0 && utf_iscomposing(utf_ptr2char(s + half)));
 	    n = ptr2cells(s + half);
-	    if (len + n > room)
+	    if (len + n > room || half == 0)
 		break;
 	    len += n;
 	    i = half;