gohugoio/hugo · error

can't iterate over a nil value

Error message

can't iterate over a nil value

What it means

After (collections.go:79-83) calls reflect.Indirect on the list; a typed-nil pointer/slice (isNil==true) hits this branch. Literal nil is caught earlier at line 66, so this specifically means a non-nil interface wrapping nil.

Source

Thrown at tpl/collections/collections.go:82

// After returns all the items after the first n items in list l.
func (ns *Namespace) After(n any, l any) (any, error) {
	if n == nil || l == nil {
		return nil, errors.New("both limit and seq must be provided")
	}

	nv, err := cast.ToIntE(n)
	if err != nil {
		return nil, err
	}

	if nv < 0 {
		return nil, errors.New("sequence bounds out of range [" + cast.ToString(nv) + ":]")
	}

	lv := reflect.ValueOf(l)
	lv, isNil := hreflect.Indirect(lv)
	if isNil {
		return nil, errors.New("can't iterate over a nil value")
	}

	switch lv.Kind() {
	case reflect.Array, reflect.Slice, reflect.String:
		// okay
	default:
		return nil, errors.New("can't iterate over " + reflect.ValueOf(l).Type().String())
	}

	if nv >= lv.Len() {
		return lv.Slice(0, 0).Interface(), nil
	}

	return lv.Slice(nv, lv.Len()).Interface(), nil
}

// Delimit takes a given list l and returns a string delimited by sep.
// If last is passed to the function, it will be used as the final delimiter.

View on GitHub (pinned to 52c9bd7908)

Solutions

1. Guard: {{ with $seq }}{{ after n . }}{{ end }}
2. Coalesce to empty slice: {{ after n (default $seq slice) }}

Example fix

// before
{{ after 2 $nilPtr }}
// after
{{ with $nilPtr }}{{ after 2 . }}{{ end }}

{{ with $seq }}
  {{ after 2 . }}
{{ end }}

{{ with $seq }}...{{ end }}

When it happens

Trigger: Passing a nil *Pages or nil pointer to a slice that is wrapped in a non-nil interface to after.

Common situations: .Params.tags typed as a pointer that is unset; a range variable that resolved to a typed nil; a section method returning nil.

Related errors

• can't iterate over a nil value
• called apply using {xt} as type {targ}
• both limit and seq must be provided
• intersect does not support slices or arrays of uncomparable
• need at least 2 arguments to append

AI-assisted analysis of gohugoio/hugo@52c9bd7908 (2026-08-09). Data as JSON: /api/errors/404f7cb06a13ad65. Report an issue: GitHub.