diff --git a/lib/internal/crypto/keygen.js b/lib/internal/crypto/keygen.js
index d1c14e547fd640..e6e787c39f512a 100644
--- a/lib/internal/crypto/keygen.js
+++ b/lib/internal/crypto/keygen.js
@@ -181,6 +181,7 @@ function parseKeyEncoding(keyType, options = kEmptyObject) {
 }
 
 const nidOnlyKeyPairs = {
+  '__proto__': null,
   'ed25519': EVP_PKEY_ED25519,
   'ed448': EVP_PKEY_ED448,
   'x25519': EVP_PKEY_X25519,
diff --git a/test/parallel/test-crypto-keygen.js b/test/parallel/test-crypto-keygen.js
index e0515c15776fc6..7911520af34481 100644
--- a/test/parallel/test-crypto-keygen.js
+++ b/test/parallel/test-crypto-keygen.js
@@ -55,6 +55,20 @@ const { hasOpenSSL3 } = require('../common/crypto');
     code: 'ERR_INVALID_ARG_VALUE',
     message: "The argument 'type' must be a supported key type. Received 'rsa2'"
   });
+
+  for (const type of ['toString', 'constructor']) {
+    assert.throws(() => generateKeyPairSync(type, {}), {
+      name: 'TypeError',
+      code: 'ERR_INVALID_ARG_VALUE',
+      message: `The argument 'type' must be a supported key type. Received '${type}'`
+    });
+
+    assert.throws(() => generateKeyPair(type, {}, common.mustNotCall()), {
+      name: 'TypeError',
+      code: 'ERR_INVALID_ARG_VALUE',
+      message: `The argument 'type' must be a supported key type. Received '${type}'`
+    });
+  }
 }
 
 {