diff --git a/extensions/default/src/DicomWebDataSource/index.ts b/extensions/default/src/DicomWebDataSource/index.ts
index d9ee04320..77df834fa 100644
--- a/extensions/default/src/DicomWebDataSource/index.ts
+++ b/extensions/default/src/DicomWebDataSource/index.ts
@@ -431,6 +431,9 @@ function createDicomWebApi(dicomWebConfig: DicomWebConfig, servicesManager) {
        * This is done recursively, for sub-sequences.
        */
       const addRetrieveBulkDataNaturalized = (naturalized, instance = naturalized) => {
+        if (!naturalized) {
+          return naturalized;
+        }
         for (const key of Object.keys(naturalized)) {
           const value = naturalized[key];