diff --git a/src/less-than-equal/validator.ts b/src/less-than-equal/validator.ts
index 0e8b50d..b540089 100644
--- a/src/less-than-equal/validator.ts
+++ b/src/less-than-equal/validator.ts
@@ -4,6 +4,7 @@ import { isPresent } from '../util/lang';
 
 export const lte = (lte: number): ValidatorFn => {
   return (control: AbstractControl): {[key: string]: boolean} => {
+    if (!lte) return null;
     if (!isPresent(lte)) return null;
     if (isPresent(Validators.required(control))) return null;
 
diff --git a/src/less-than/validator.ts b/src/less-than/validator.ts
index 7a295b1..c153cae 100644
--- a/src/less-than/validator.ts
+++ b/src/less-than/validator.ts
@@ -4,6 +4,7 @@ import { isPresent } from '../util/lang';
 
 export const lt = (lt: number): ValidatorFn => {
   return (control: AbstractControl): {[key: string]: boolean} => {
+    if (!lt) return null;
     if (!isPresent(lt)) return null;
     if (isPresent(Validators.required(control))) return null;