diff --git a/overlord/src/app/issue/issue.component.ts b/overlord/src/app/issue/issue.component.ts
index 93ef52a2..38d65318 100644
--- a/overlord/src/app/issue/issue.component.ts
+++ b/overlord/src/app/issue/issue.component.ts
@@ -193,10 +193,10 @@ export class IssueComponent implements OnInit, AfterViewInit, OnDestroy {
       this.voucher.inventories.push(
         new Inventory({
           quantity,
-          rate: this.batch.rate,
-          tax: this.batch.tax,
-          discount: this.batch.discount,
-          amount: quantity * this.batch.rate * (1 + this.batch.tax) * (1 - this.batch.discount),
+          rate: +this.batch.rate,
+          tax: +this.batch.tax,
+          discount: +this.batch.discount,
+          amount: quantity * +this.batch.rate * (1 + +this.batch.tax) * (1 - +this.batch.discount),
           batch: this.batch,
         }),
       );