diff --git a/_includes/nav.html b/_includes/nav.html
index 748b6ce..c9bcbda 100644
--- a/_includes/nav.html
+++ b/_includes/nav.html
@@ -4,11 +4,15 @@
| where_exp:"item", "item.title != nil" -%}
{%- comment -%}
- A nav_order value can be a number or a string.
- Numbers are sorted by their values, before strings.
- An omitted nav_order value is equivalent to the title value,
- except that a numerical title value is treated as a string.
- The case-sensitivity of string sorting is determined by site.nav_sort.
+ The values of `title` and `nav_order` can be numbers or strings.
+ Jekyll gives build failures when sorting on mixtures of different types,
+ so numbers and strings need to be sorted separately.
+
+ Here, numbers are sorted by their values, and come before all strings.
+ An omitted `nav_order` value is equivalent to the page's `title` value
+ (except that a numerical `title` value is treated as a string).
+
+ The case-sensitivity of string sorting is determined by `site.nav_sort`.
{%- endcomment -%}
{%- assign string_ordered_pages = included_pages