diff --git a/lib/helpers/isAsyncFunction.js b/lib/helpers/isAsyncFunction.js
index 81846e24c4c..ecd2872af0e 100644
--- a/lib/helpers/isAsyncFunction.js
+++ b/lib/helpers/isAsyncFunction.js
@@ -8,4 +8,4 @@ module.exports = function isAsyncFunction(v) {
   }
 
   return inspect(v).startsWith('[AsyncFunction:');
-}
\ No newline at end of file
+};
\ No newline at end of file
diff --git a/lib/schematype.js b/lib/schematype.js
index 5032dc3e663..a26b1d71ec4 100644
--- a/lib/schematype.js
+++ b/lib/schematype.js
@@ -1270,48 +1270,6 @@ SchemaType.prototype.doValidate = function(value, fn, scope, options) {
   }
 };
 
-/*!
- * Handle async validators
- */
-
-function asyncValidate(validator, scope, value, props, cb) {
-  let called = false;
-  const returnVal = validator.call(scope, value, function(ok, customMsg) {
-    if (called) {
-      return;
-    }
-    called = true;
-    if (customMsg) {
-      props.message = customMsg;
-    }
-    cb(ok, props);
-  });
-  if (typeof returnVal === 'boolean') {
-    called = true;
-    cb(returnVal, props);
-  } else if (returnVal && typeof returnVal.then === 'function') {
-    // Promise
-    returnVal.then(
-      function(ok) {
-        if (called) {
-          return;
-        }
-        called = true;
-        cb(ok, props);
-      },
-      function(error) {
-        if (called) {
-          return;
-        }
-        called = true;
-
-        props.reason = error;
-        props.message = error.message;
-        cb(false, props);
-      });
-  }
-}
-
 /**
  * Performs a validation of `value` using the validators declared for this SchemaType.
  *
diff --git a/package.json b/package.json
index 465875ef2e2..b68254dbe42 100644
--- a/package.json
+++ b/package.json
@@ -128,7 +128,7 @@
       "mocha-no-only"
     ],
     "parserOptions": {
-      "ecmaVersion": 2015
+      "ecmaVersion": 2020
     },
     "env": {
       "node": true,
diff --git a/test/typescript/discriminator.ts b/test/typescript/discriminator.ts
index 9b80adae4b9..052e3c3ba3c 100644
--- a/test/typescript/discriminator.ts
+++ b/test/typescript/discriminator.ts
@@ -43,25 +43,25 @@ function test(): void {
 
   const cardDbSchema: Schema = new Schema(
     cardDbBaseSchemaDefinition,
-    cardDbSchemaOptions,
+    cardDbSchemaOptions
   );
 
   const cardDbModel: Model<CardDb> = mongoose.model<CardDb>(
     'Card',
     cardDbSchema,
-    'card',
+    'card'
   );
 
   const landDbAdditionalPropertiesSchemaDefinition: SchemaDefinition = {};
 
   const landDbSchema: Schema = new Schema(
-    landDbAdditionalPropertiesSchemaDefinition,
+    landDbAdditionalPropertiesSchemaDefinition
   );
 
   const landDbModel: Model<LandDb> = cardDbModel.discriminator<LandDb>(
     'Land',
     landDbSchema,
-    CardType.Land,
+    CardType.Land
   );
 
   const sampleLandDb: LandDb = new landDbModel({