diff --git a/src/models/domain/cipher.ts b/src/models/domain/cipher.ts
index 1c3040edc8..1bbdd7675d 100644
--- a/src/models/domain/cipher.ts
+++ b/src/models/domain/cipher.ts
@@ -178,7 +178,7 @@ export class Cipher extends Domain {
         c.edit = this.edit;
         c.organizationUseTotp = this.organizationUseTotp;
         c.favorite = this.favorite;
-        c.revisionDate = this.revisionDate.toISOString();
+        c.revisionDate = this.revisionDate != null ? this.revisionDate.toISOString() : null;
         c.type = this.type;
         c.collectionIds = this.collectionIds;