diff --git a/src/arabic.c b/src/arabic.c
index 8c1f64c..72c64b5 100644
--- a/src/arabic.c
+++ b/src/arabic.c
@@ -1066,7 +1066,7 @@
 
     if (curr_c != c && ccp != NULL)
     {
-	char_u buf[MB_MAXBYTES];
+	char_u buf[MB_MAXBYTES + 1];
 
 	/* Update the first byte of the character. */
 	(*mb_char2bytes)(curr_c, buf);