diff --git a/ext/view/theme.php b/ext/view/theme.php
index 671af819..bb830225 100644
--- a/ext/view/theme.php
+++ b/ext/view/theme.php
@@ -22,6 +22,8 @@ class ViewTheme extends Themelet {
 	var $pin = null;
 
 	protected function build_pin($image_id) {
+		assert(is_numeric($image_id));
+
 		if(!is_null($this->pin)) {
 			return $this->pin;
 		}
diff --git a/themes/danbooru/view.theme.php b/themes/danbooru/view.theme.php
index adbf3e6f..6f77010a 100644
--- a/themes/danbooru/view.theme.php
+++ b/themes/danbooru/view.theme.php
@@ -4,10 +4,10 @@ class CustomViewTheme extends ViewTheme {
 	public function display_page($page, $image, $editor_parts) {
 		$page->set_title("Image {$image->id}: ".html_escape($image->get_tag_list()));
 		$page->set_heading(html_escape($image->get_tag_list()));
-		$page->add_block(new Block("Navigation", $this->build_navigation($image), "left", 0));
+		$page->add_block(new Block("Navigation", $this->build_navigation($image->id), "left", 0));
 		$page->add_block(new Block("Statistics", $this->build_stats($image), "left", 10));
 		$page->add_block(new Block(null, $this->build_image_editor($image, $editor_parts), "main", 10));
-		$page->add_block(new Block(null, $this->build_pin($image), "main", 11));
+		$page->add_block(new Block(null, $this->build_pin($image->id), "main", 11));
 	}
 
 	private function build_stats($image) {