diff --git a/frontend/main.ts b/frontend/main.ts
index 949f557..001a585 100644
--- a/frontend/main.ts
+++ b/frontend/main.ts
@@ -62,18 +62,18 @@ function selectBoatChange() {
   choiceObjects[shipmasterSelect.id] = shipmasterChoice;
 }
 
-function setMaxAmountRowers(rowers){
+function setMaxAmountRowers(rowers: number){
 	  let curSelection = choiceObjects['newrower'].getValue(true);
-	  let amount_to_delete = curSelection.length - rowers;
-	  if (amount_to_delete > 0){
-		let to_delete = curSelection.slice(-amount_to_delete);
-		for (let del of to_delete) {
-			choiceObjects['newrower'].removeActiveItemsByValue(del);
-		}
-	  }
+	  	let amount_to_delete = (<any>curSelection).length - rowers;
+	  	if (amount_to_delete > 0){
+	  	      let to_delete = (<any>curSelection).slice(-amount_to_delete);
+	  	      for (let del of to_delete) {
+	  	      	choiceObjects['newrower'].removeActiveItemsByValue(del);
+	  	      }
+	  	}
 
 	  choiceObjects['newrower'].config.maxItemCount = rowers;
-		const only_steering =  <HTMLSelectElement>document.querySelector('#shipmaster_only_steering');
+	  const only_steering =  <HTMLSelectElement>document.querySelector('#shipmaster_only_steering');
 	  if (rowers === 0) {
 		choiceObjects['newrower'].disable()
 		only_steering.disabled = true;