diff --git a/ext/pools/main.php b/ext/pools/main.php
index 93e395f2..d4d38de7 100644
--- a/ext/pools/main.php
+++ b/ext/pools/main.php
@@ -473,7 +473,7 @@ class Pools extends Extension
                 $pools = $database->get_pairs("SELECT id,title FROM pools WHERE user_id=:id ORDER BY title", ["id" => $user->id]);
             }
             if (count($pools) > 0) {
-                $event->add_part($this->theme->get_adder_html($event->image, $pools));
+                $event->add_part((string)$this->theme->get_adder_html($event->image, $pools));
             }
         }
     }
diff --git a/ext/pools/theme.php b/ext/pools/theme.php
index 50c83516..7f9e4ea2 100644
--- a/ext/pools/theme.php
+++ b/ext/pools/theme.php
@@ -42,14 +42,15 @@ class PoolsTheme extends Themelet
         }
     }
 
-    public function get_adder_html(Image $image, array $pools): string
+    public function get_adder_html(Image $image, array $pools): HTMLElement
     {
-        $selector = $this->build_selector("pool_id", $pools);
-        return "\n" . make_form(make_link("pool/add_post")) . $selector . "
-            <input type='hidden' name='image_id' value='{$image->id}'>
-            <input type='submit' value='Add Post to Pool'>
-            </form>
-        ";
+        $form = make_form_microhtml(make_link("pool/add_post"));
+
+        $form->appendChild($this->build_selector("pool_id", $pools));
+        $form->appendChild(INPUT(["type"=>"hidden", "name"=>"image_id", "value"=>$image->id]));
+        $form->appendChild(INPUT(["type"=>"submit", "value"=>"Add Post to Pool"]));
+
+        return $form;
     }
 
     /**