diff --git a/lib/model/mlp.js b/lib/model/mlp.js
index a42a0e09f..a10f834e9 100644
--- a/lib/model/mlp.js
+++ b/lib/model/mlp.js
@@ -87,7 +87,7 @@ class MLP {
 export class MLPClassifier {
 	/**
 	 * @param {number[]} hidden_sizes Sizes of hidden layers
-	 * @param {'identity', 'elu', 'gaussian', 'leaky_relu', 'relu', 'sigmoid', 'softplus', 'softsign', 'tanh'} [activation=tanh] Activation name
+	 * @param {'identity' | 'elu' | 'gaussian' | 'leaky_relu' | 'relu' | 'sigmoid' | 'softplus' | 'softsign' | 'tanh'} [activation=tanh] Activation name
 	 */
 	constructor(hidden_sizes, activation = 'tanh') {
 		this._hidden_sizes = hidden_sizes
@@ -212,7 +212,7 @@ export class MLPClassifier {
 export class MLPRegressor {
 	/**
 	 * @param {number[]} hidden_sizes Sizes of hidden layers
-	 * @param {'identity', 'elu', 'gaussian', 'leaky_relu', 'relu', 'sigmoid', 'softplus', 'softsign', 'tanh'} [activation=tanh] Activation name
+	 * @param {'identity' | 'elu' | 'gaussian' | 'leaky_relu' | 'relu' | 'sigmoid' | 'softplus' | 'softsign' | 'tanh'} [activation=tanh] Activation name
 	 */
 	constructor(hidden_sizes, activation = 'tanh') {
 		this._hidden_sizes = hidden_sizes