diff --git a/frontend/src/routes/guest/register/steps/register.tsx b/frontend/src/routes/guest/register/steps/register.tsx
index 6688df1a3b3855ad57c30b592a4c22a7a9c1653c..6b3b195df385ec1bbe90439e259dfda9f79dfe83 100644
--- a/frontend/src/routes/guest/register/steps/register.tsx
+++ b/frontend/src/routes/guest/register/steps/register.tsx
@@ -57,13 +57,12 @@ const GuestRegisterStep = forwardRef(
     const { i18n, t } = useTranslation(['common'])
     const { nextHandler, initialGuestData, registerData } = props
     const { showGenderFieldForGuest } = useContext(FeatureContext)
+    const defaultCountryCode = 'NO'
 
     // For select-components it seems to be easier to tie them to a state
     // and then handle the updating of the form using this, than to tie the
     // components directly to the form-field using useForm
-    const [countryCode, setCountryCode] = useState<
-      CountryCallingCode | undefined
-    >('NO')
+    const [countryCode, setCountryCode] = useState<CountryCallingCode>(defaultCountryCode)
     const [passportNationality, setPassportNationality] = useState<
       string | undefined
     >(undefined)
@@ -108,6 +107,17 @@ const GuestRegisterStep = forwardRef(
       }
     }
 
+    if (!registerData || !registerData.mobilePhoneCountry) {
+      // If there is no country code set in the registered data
+      // then set the default value. This is necessary even though
+      // the country code is set in a state variable above, because
+      // that does not cause the country code to be added to the
+      // form values by itself. If it was not set here it would be
+      // blank in the form even though the default value is shown
+      // in the select menu
+      setValue('mobilePhoneCountry', defaultCountryCode)
+    }
+
     const validatePhoneNumber = (
       countryCodeCallingCode: CountryCallingCode | undefined,
       phoneNumberToValidate: string
@@ -203,13 +213,12 @@ const GuestRegisterStep = forwardRef(
     }
 
     const handleCountryCodeChange = (event: SelectChangeEvent) => {
-      if (event.target.value) {
-        const countryCodeType = event.target.value as CountryCode
-        setCountryCode(countryCodeType)
-        setValue('mobilePhoneCountry', countryCodeType)
-      } else {
-        setCountryCode(undefined)
-      }
+      // There should always be a value in the event since it is
+      // not possible to select a blank field in the select menu
+      // for country codes
+      const countryCodeType = event.target.value as CountryCode
+      setCountryCode(countryCodeType)
+      setValue('mobilePhoneCountry', countryCodeType)
     }
 
     const handleMobilePhoneChange = (value: any) => {
@@ -506,7 +515,7 @@ const GuestRegisterStep = forwardRef(
                   displayEmpty
                   onChange={handleCountryCodeChange}
                   label={t('input.countryCallingCode')}
-                  value={countryCode ? countryCode.toString() : 'NO'}
+                  value={countryCode ? countryCode.toString() : defaultCountryCode}
                   renderValue={(selected: any) => {
                     if (!selected || selected.length === 0) {
                       return t('input.countryCallingCode')