diff --git a/frontend/main.ts b/frontend/main.ts
index 6e9f387..5a4d8ff 100644
--- a/frontend/main.ts
+++ b/frontend/main.ts
@@ -132,13 +132,21 @@ function setMaxAmountRowers(name: string, rowers: number) {
     let shipmaster = <HTMLElement>document.querySelector('#shipmaster-newrowerjs');
     let steering_person = <HTMLElement>document.querySelector('#steering_person-newrowerjs');
     if (rowers == 1){
-	shipmaster.parentNode.classList.add('hidden');
-	steering_person.parentNode.classList.add('hidden');
+	if (shipmaster.parentNode) {
+		(<HTMLElement>shipmaster.parentNode).classList.add('hidden');
+	}
+	if (steering_person.parentNode){
+		(<HTMLElement>steering_person.parentNode).classList.add('hidden');
+	}
     }else{
-	shipmaster.parentNode.classList.remove('hidden');
+	if (shipmaster.parentNode){
+		(<HTMLElement>shipmaster.parentNode).classList.remove('hidden');
+	}
 	shipmaster.setAttribute('required', 'required');
 
-	steering_person.parentNode.classList.remove('hidden');
+	if (steering_person.parentNode){
+		(<HTMLElement>steering_person.parentNode).classList.remove('hidden');
+	}
 	steering_person.setAttribute('required', 'required');
     }
   }