diff --git a/token-validator/domain.go b/token-validator/domain.go
index 3679e2d..bb39b49 100644
--- a/token-validator/domain.go
+++ b/token-validator/domain.go
@@ -121,7 +121,7 @@ func parseKnotZoneRead(args ...string) (rr []Entry, err error) {
 }
 
 func (student Student) myAssociatedDomain() (string) {
-	return fmt.Sprintf("%s.%s.", student.Login, AssociatedDomainSuffix)
+	return fmt.Sprintf("%s.%s.", strings.Replace(student.Login, "_", "-", -1), AssociatedDomainSuffix)
 }
 
 func (student Student) GetAssociatedDomains() (ds []string) {
@@ -176,7 +176,7 @@ func (student Student) AddAssociatedDomains() (err error) {
 
 
 func (student Student) MyDelegatedDomain() (string) {
-	return fmt.Sprintf("%s.%s.", student.Login, DelegatedDomainSuffix)
+	return fmt.Sprintf("%s.%s.", strings.Replace(student.Login, "_", "-", -1), DelegatedDomainSuffix)
 }
 
 func (student Student) getRRDelegatedDomain(dn string, rr string) (rrs []Entry, err error) {