diff --git a/src/classes/Plan.php b/src/classes/Plan.php
index 658c50b..0faf3a9 100644
--- a/src/classes/Plan.php
+++ b/src/classes/Plan.php
@@ -146,6 +146,11 @@ public function items(): Collection
 				throw new InvalidArgumentException('Invalid item ' . $num);
 			}
 
+			// skip dummy items (e.g. radiator from the room designer)
+			if (is_string($item['id'] ?? null) !== true) {
+				continue;
+			}
+
 			$items[] = new Configuration($item);
 		}
 
diff --git a/tests/Roomle/ConfigurationTest.php b/tests/Roomle/ConfigurationTest.php
index 5b2b4d7..d5b7075 100644
--- a/tests/Roomle/ConfigurationTest.php
+++ b/tests/Roomle/ConfigurationTest.php
@@ -15,7 +15,7 @@ public function setUp(): void
 		new App([
 			'request' => [
 				'body' => [
-					'roomle-configuration' => '{"id": null, "items": [{"depth": 123}]}'
+					'roomle-configuration' => '{"id": null, "items": [{"id": "some-id", "depth": 123}]}'
 				]
 			],
 			'urls' => [
@@ -56,11 +56,13 @@ public function testConfiguratorUrl_Invalid()
 	public function testConstruct_Array()
 	{
 		$configuration = new Configuration([
+			'id'    => 'some-id',
 			'depth' => 1337
 		]);
 		$this->assertSame(1337, $configuration->depth());
 
 		$configuration = Configuration::lazyInstance([
+			'id'    => 'some-id',
 			'depth' => 1337
 		]);
 		$this->assertSame(1337, $configuration->depth());
@@ -91,7 +93,7 @@ public function testConstruct_RequestInvalid()
 	 */
 	public function testConstruct_String()
 	{
-		$configuration = Configuration::lazyInstance('{"items": [{"depth": 1337}]}');
+		$configuration = Configuration::lazyInstance('{"items": [{"id": "some-id", "depth": 1337}]}');
 		$this->assertSame(1337, $configuration->depth());
 	}
 
diff --git a/tests/Roomle/PlanTest.php b/tests/Roomle/PlanTest.php
index b4ba0ef..c449a0a 100644
--- a/tests/Roomle/PlanTest.php
+++ b/tests/Roomle/PlanTest.php
@@ -142,6 +142,10 @@ public function testGroupedItems()
 				[
 					'id'    => 'some:item1',
 					'depth' => 123
+				],
+				[
+					'id'    => null,
+					'label' => 'Radiator'
 				]
 			]
 		]);
@@ -207,6 +211,10 @@ public function testItems()
 				[
 					'id'    => 'some:item1',
 					'depth' => 123
+				],
+				[
+					'id'    => null,
+					'label' => 'Radiator'
 				]
 			]
 		]);