diff --git a/src/Forms/Container.php b/src/Forms/Container.php
index b0903424e..55c4724f2 100644
--- a/src/Forms/Container.php
+++ b/src/Forms/Container.php
@@ -267,6 +267,9 @@ public function addComponent(
 		?string $name,
 		string $insertBefore = null,
 	): static {
+		if (!$component instanceof Control && !$component instanceof self) {
+			throw new Nette\InvalidStateException("Component '$name' of type " . gettype($component) . ' is not intended to be used in the form.');
+		}
 		parent::addComponent($component, $name, $insertBefore);
 		if ($this->currentGroup !== null) {
 			$this->currentGroup->add($component);