diff --git a/glib/gutf8.c b/glib/gutf8.c
index a4368d5f1..bb9d6fba0 100644
--- a/glib/gutf8.c
+++ b/glib/gutf8.c
@@ -437,7 +437,7 @@ g_utf8_pointer_to_offset (const gchar *str,
  * must be valid UTF-8 encoded text. (Use g_utf8_validate() on all
  * text before trying to use UTF-8 utility functions with it.)
  * 
- * Note you must ensure @dest is at least 4 * @n to fit the
+ * Note you must ensure @dest is at least 4 * @n + 1 to fit the
  * largest possible UTF-8 characters
  *
  * Returns: (transfer none): @dest