diff --git a/src/components/Register.vue b/src/components/Register.vue
index 02345bf..9622b5a 100644
--- a/src/components/Register.vue
+++ b/src/components/Register.vue
@@ -225,7 +225,7 @@ let provide_address = ref(false);
 let agb_accepted = ref(false);
 // 
 const state = reactive({
-  submit_enabled: computed(() => agb_accepted.value === true && isEmail(userdetails.value.mail)
+  submit_enabled: computed(() => agb_accepted.value === true && (isMobilePhone(userdetails.value.phone) || !userdetails.value.phone.trim()) && isEmail(userdetails.value.mail)
     && userdetails.value.firstname
     && userdetails.value.lastname && (provide_address.value === false || provide_address.value === true && (userdetails.value.address.street.trim() && userdetails.value.address.city.trim() && isPostalCode(userdetails.value.address.zipcode, "DE"))))
 })