diff --git a/libraries/stdlib/js-ir/builtins/Primitives.kt b/libraries/stdlib/js-ir/builtins/Primitives.kt
index 5904e6393fa..34356b6e022 100644
--- a/libraries/stdlib/js-ir/builtins/Primitives.kt
+++ b/libraries/stdlib/js-ir/builtins/Primitives.kt
@@ -218,6 +218,10 @@ public class Byte private constructor() : Number(), Comparable<Byte> {
      * The resulting `Double` value represents the same numerical value as this `Byte`.
      */
     public override fun toDouble(): Double
+
+    public override fun equals(other: Any?): Boolean
+    public override fun hashCode(): Int
+    public override fun toString(): String
 }
 
 /**
@@ -428,6 +432,10 @@ public class Short private constructor() : Number(), Comparable<Short> {
      * The resulting `Double` value represents the same numerical value as this `Short`.
      */
     public override fun toDouble(): Double
+
+    public override fun equals(other: Any?): Boolean
+    public override fun hashCode(): Int
+    public override fun toString(): String
 }
 
 /**
@@ -657,6 +665,10 @@ public class Int private constructor() : Number(), Comparable<Int> {
      * The resulting `Double` value represents the same numerical value as this `Int`.
      */
     public override fun toDouble(): Double
+
+    public override fun equals(other: Any?): Boolean
+    public override fun hashCode(): Int
+    public override fun toString(): String
 }
 
 /**
@@ -863,6 +875,10 @@ public class Float private constructor() : Number(), Comparable<Float> {
      * The resulting `Double` value represents the same numerical value as this `Float`.
      */
     public override fun toDouble(): Double
+
+    public override fun equals(other: Any?): Boolean
+    public override fun hashCode(): Int
+    public override fun toString(): String
 }
 
 /**
@@ -1071,5 +1087,9 @@ public class Double private constructor() : Number(), Comparable<Double> {
     public override fun toFloat(): Float
     /** Returns this value. */
     public override fun toDouble(): Double
+
+    public override fun equals(other: Any?): Boolean
+    public override fun hashCode(): Int
+    public override fun toString(): String
 }
 
diff --git a/libraries/stdlib/js-ir/builtins/Throwable.kt b/libraries/stdlib/js-ir/builtins/Throwable.kt
index 83fdc12aedf..88f67a839ff 100644
--- a/libraries/stdlib/js-ir/builtins/Throwable.kt
+++ b/libraries/stdlib/js-ir/builtins/Throwable.kt
@@ -1,5 +1,5 @@
 /*
- * Copyright 2010-2019 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Copyright 2010-2020 JetBrains s.r.o. and Kotlin Programming Language contributors.
  * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
  */
 
@@ -13,11 +13,16 @@ package kotlin
  */
 @JsName("Error")
 public external open class Throwable {
-    open val message: String?
-    open val cause: Throwable?
+    public open val message: String?
+    public open val cause: Throwable?
 
-    constructor(message: String?, cause: Throwable?)
-    constructor(message: String?)
-    constructor(cause: Throwable?)
-    constructor()
+    public constructor(message: String?, cause: Throwable?)
+    public constructor(message: String?)
+    public constructor(cause: Throwable?)
+    public constructor()
+
+    // TODO: add specialized version to runtime
+//    public override fun equals(other: Any?): Boolean
+//    public override fun hashCode(): Int
+    public override fun toString(): String
 }
\ No newline at end of file