diff --git a/ext/node/polyfills/internal/crypto/keys.ts b/ext/node/polyfills/internal/crypto/keys.ts
index 8cb9ab6906f11b..ca22e12c6197fd 100644
--- a/ext/node/polyfills/internal/crypto/keys.ts
+++ b/ext/node/polyfills/internal/crypto/keys.ts
@@ -4,6 +4,13 @@
 // TODO(petamoriken): enable prefer-primordials for node polyfills
 // deno-lint-ignore-file prefer-primordials
 
+import { primordials } from "ext:core/mod.js";
+
+const {
+  ObjectDefineProperties,
+  SymbolToStringTag,
+} = primordials;
+
 import {
   op_node_create_private_key,
   op_node_create_public_key,
@@ -209,6 +216,14 @@ export class KeyObject {
   }
 }
 
+ObjectDefineProperties(KeyObject.prototype, {
+  [SymbolToStringTag]: {
+    __proto__: null,
+    configurable: true,
+    value: "KeyObject",
+  },
+});
+
 export interface JsonWebKeyInput {
   key: JsonWebKey;
   format: "jwk";