diff --git a/src/lib/encode-conversions.ts b/src/lib/encode-conversions.ts
index df54f09..dbd4a81 100644
--- a/src/lib/encode-conversions.ts
+++ b/src/lib/encode-conversions.ts
@@ -108,8 +108,8 @@ export const convertObservation: ConvertFunction<'observation'> = (
   let presetRef
   if (mapeoDoc.presetRef) {
     presetRef = {
-      docId: Buffer.from(mapeoDoc.presetRef?.docId, 'hex'),
-      versionId: parseVersionId(mapeoDoc.presetRef?.versionId),
+      docId: Buffer.from(mapeoDoc.presetRef.docId, 'hex'),
+      versionId: parseVersionId(mapeoDoc.presetRef.versionId),
     }
   }