diff --git a/frontend/src/app/validators/keywords.validator.ts b/frontend/src/app/validators/keywords.validator.ts
index e505fea..26cf40f 100644
--- a/frontend/src/app/validators/keywords.validator.ts
+++ b/frontend/src/app/validators/keywords.validator.ts
@@ -1,7 +1,7 @@
 import {AbstractControl} from '@angular/forms';
 
 export function keywordsValidator(control: AbstractControl): { [key: string]: any } | null {
-  if (control.value === undefined) {
+  if (control.value === null) {
     return null;
   }
   let split: string[];