diff --git a/src/LookupResult/CompanyLookupResult.php b/src/LookupResult/CompanyLookupResult.php
index cf21e9e..1ab4ef0 100644
--- a/src/LookupResult/CompanyLookupResult.php
+++ b/src/LookupResult/CompanyLookupResult.php
@@ -352,7 +352,7 @@ public function setAddress(string $address): void {
    *   The field value or the empty string if the field does not exist.
    */
   public function getFieldValue(string $field): mixed {
-    if (property_exists($this, $field)) {
+    if (property_exists($this, $field) && isset($this->{$field})) {
       return $this->{$field};
     }
 
diff --git a/src/LookupResult/CprLookupResult.php b/src/LookupResult/CprLookupResult.php
index 1b9f67c..0b254d3 100644
--- a/src/LookupResult/CprLookupResult.php
+++ b/src/LookupResult/CprLookupResult.php
@@ -672,7 +672,7 @@ public function hasGuardian(string $cpr): bool {
    *   The value of the field or the empty string.
    */
   public function getFieldValue(string $field): mixed {
-    if (property_exists($this, $field)) {
+    if (property_exists($this, $field) && isset($this->{$field})) {
       return $this->{$field};
     }