diff --git a/src/Services/ImportExportSystem/PartKeeprImporter/PKDatastructureImporter.php b/src/Services/ImportExportSystem/PartKeeprImporter/PKDatastructureImporter.php
index 9e674f05..ec23d34b 100644
--- a/src/Services/ImportExportSystem/PartKeeprImporter/PKDatastructureImporter.php
+++ b/src/Services/ImportExportSystem/PartKeeprImporter/PKDatastructureImporter.php
@@ -152,7 +152,7 @@ class PKDatastructureImporter
     public function importPartCustomStates(array $data): int
     {
         if (!isset($data['partcustomstate'])) {
-            throw new \RuntimeException('$data must contain a "partcustomstate" key!');
+            return 0; //Not all PartKeepr installations have custom states
         }
 
         $partCustomStateData = $data['partcustomstate'];
diff --git a/src/Services/ImportExportSystem/PartKeeprImporter/PKPartImporter.php b/src/Services/ImportExportSystem/PartKeeprImporter/PKPartImporter.php
index ab06a134..cab5a49b 100644
--- a/src/Services/ImportExportSystem/PartKeeprImporter/PKPartImporter.php
+++ b/src/Services/ImportExportSystem/PartKeeprImporter/PKPartImporter.php
@@ -91,7 +91,10 @@ class PKPartImporter
                     $this->setAssociationField($entity, 'partUnit', MeasurementUnit::class, $part['partUnit_id']);
                 }
 
-                $this->setAssociationField($entity, 'partCustomState', MeasurementUnit::class, $part['partCustomState_id']);
+                if (isset($part['partCustomState_id'])) {
+                    $this->setAssociationField($entity, 'partCustomState', MeasurementUnit::class,
+                        $part['partCustomState_id']);
+                }
 
                 //Create a part lot to store the stock level and location
                 $lot = new PartLot();