unsupported type in paginate from slice, got %T instead of P

Error message

unsupported type in paginate from slice, got %T instead of PageGroup

What it means

Returned by ToPagesGroup when a []any passed to .Paginate starts with a PageGroup (so Hugo commits to treating it as grouped pages) but a later element is a different type. Grouped pagination requires a homogeneous slice of PageGroup values.

Source

Thrown at resources/page/pagegroup.go:453

	case nil:
		return nil, true, nil
	case PagesGroup:
		return v, true, nil
	case []PageGroup:
		return PagesGroup(v), true, nil
	case []any:
		l := len(v)
		if l == 0 {
			break
		}
		switch v[0].(type) {
		case PageGroup:
			pagesGroup := make(PagesGroup, l)
			for i, ipg := range v {
				if pg, ok := ipg.(PageGroup); ok {
					pagesGroup[i] = pg
				} else {
					return nil, false, fmt.Errorf("unsupported type in paginate from slice, got %T instead of PageGroup", ipg)
				}
			}
			return pagesGroup, true, nil
		}
	}

	return nil, false, nil
}

View on GitHub ↗ (pinned to 8a468df065)

Solutions

Pass the GroupBy result directly to .Paginate: `{{ $p := .Paginate (.Pages.GroupByDate "2006") }}`
If mixing data, paginate plain Pages instead and group inside the pager loop
Check any append/slice manipulation for elements that are not PageGroup

Example fix

// before
{{ $pag := .Paginate (slice (index $groups 0) .Site.RegularPages) }}
// after
{{ $pag := .Paginate (.Pages.GroupByDate "2006") }}

Defensive patterns

Strategy: type-guard

Validate before calling

{{ $grouped := .Pages.GroupByDate "2006" }}{{ $pag := .Paginate $grouped }}

Type guard

// only slices whose elements are PageGroup are valid: use output of GroupBy* directly, never a hand-built slice

Prevention

Pass either a Pages collection or the direct result of a GroupBy* method to .Paginate — never a heterogeneous or manually assembled slice
Avoid transforming grouped results with slice/append/where in ways that change element types before paginating
Keep the GroupBy call adjacent to the Paginate call in the template so the type is obvious

When it happens

Trigger: Calling `.Paginate` with a hand-built slice whose first element is a PageGroup but later elements are Pages, maps, or strings, e.g. `{{ .Paginate (slice $group1 $somePage) }}` — element 0 passes the type switch, element N fails the per-element assertion.

Common situations: Templates that append extra items to the result of .Pages.GroupBy before paginating, merging grouped and ungrouped collections, or theme code using `append`/`slice` on grouped data incorrectly.

Related errors

AI-assisted analysis of gohugoio/hugo@8a468df065 (2026-07-31). Data as JSON: /data/errors/b14e852efa3289ce.json. Report an issue: GitHub ↗.