diff --git a/page.go b/page.go
index b62fddc..5679bbd 100644
--- a/page.go
+++ b/page.go
@@ -199,6 +199,9 @@ func (p *Page) process(cfg *Site, task *Task) error {
 				tmplName = "index"
 			}
 			tmpl, ok := cfg.templates.FindTemplate(p.FilePath, tmplName+task.TemplateExt)
+			if !ok && p.Template != "" {
+				return fmt.Errorf("failed to generate index page %q: template %q specified in frontmatter but not found", p.Path, tmplName)
+			}
 			if ok {
 				var b strings.Builder
 				if err := tmpl.Execute(&b, p); err != nil {
@@ -216,6 +219,9 @@ func (p *Page) process(cfg *Site, task *Task) error {
 			}
 			var b strings.Builder
 			tmpl, ok := cfg.templates.FindTemplate(p.FilePath, tmplName+task.TemplateExt)
+			if !ok && p.Pages[i].Template != "" {
+				return fmt.Errorf("failed to generate page %q: template %q specified in frontmatter but not found", p.Pages[i].Path, tmplName)
+			}
 			if ok {
 				if err := tmpl.Execute(&b, p.Pages[i]); err != nil {
 					return err