diff --git a/src/MongoDB.ts b/src/MongoDB.ts
index 43184f3..2ff1077 100644
--- a/src/MongoDB.ts
+++ b/src/MongoDB.ts
@@ -44,7 +44,7 @@ export const parseValidationError = (error: MongoServerError) =>
 {
     if (error.code !== 121 || !error.errInfo)
         throw new Error('Not a validation error');
-    const rule = error.errInfo.details.schemaRulesNotSatisfied;
+    const [ rule ] = error.errInfo.details.schemaRulesNotSatisfied;
     const missing = rule.missingProperties as string[];
     const required = rule.specifiedAs.required as string[];
     return { missing, required };