diff --git a/js/js.tests/test/org/jetbrains/kotlin/js/test/semantics/BoxJsTestGenerated.java b/js/js.tests/test/org/jetbrains/kotlin/js/test/semantics/BoxJsTestGenerated.java
index d7a4aafdb43..620ae5dde6b 100644
--- a/js/js.tests/test/org/jetbrains/kotlin/js/test/semantics/BoxJsTestGenerated.java
+++ b/js/js.tests/test/org/jetbrains/kotlin/js/test/semantics/BoxJsTestGenerated.java
@@ -2692,6 +2692,11 @@ public class BoxJsTestGenerated extends AbstractBoxJsTest {
                 runTest("js/js.translator/testData/box/expression/try/exceptionToString.kt");
             }
 
+            @TestMetadata("exceptionToString_legacy.kt")
+            public void testExceptionToString_legacy() throws Exception {
+                runTest("js/js.translator/testData/box/expression/try/exceptionToString_legacy.kt");
+            }
+
             @TestMetadata("kt22053.kt")
             public void testKt22053() throws Exception {
                 runTest("js/js.translator/testData/box/expression/try/kt22053.kt");
diff --git a/js/js.translator/testData/box/expression/evaluationOrder/throwableDelegation.kt b/js/js.translator/testData/box/expression/evaluationOrder/throwableDelegation.kt
index 85338a7ca99..ebb47e3a26d 100644
--- a/js/js.translator/testData/box/expression/evaluationOrder/throwableDelegation.kt
+++ b/js/js.translator/testData/box/expression/evaluationOrder/throwableDelegation.kt
@@ -23,10 +23,10 @@ class MyException2(i1: String, i2: String, m: String? = null, t: Throwable? = nu
 
 
 fun box(): String {
-    check(MyException1("1", "2"), "MyException1: null")
+    check(MyException1("1", "2"), "MyException1")
     check(MyException1("3", "4", "aaa"), "MyException1: aaa")
     check(MyException1("5", "6", t = Throwable("bbb")), "MyException1: Throwable: bbb")
-    check(MyException2("7", "8"), "MyException2: null")
+    check(MyException2("7", "8"), "MyException2")
     check(MyException2("9", "0", "ccc"), "MyException2: ccc")
     check(MyException2("A", "B", t = Throwable("ddd")), "MyException2: Throwable: ddd")
 
diff --git a/js/js.translator/testData/box/expression/try/exceptionToString.kt b/js/js.translator/testData/box/expression/try/exceptionToString.kt
index ec84d0b1f8f..504daee1e02 100644
--- a/js/js.translator/testData/box/expression/try/exceptionToString.kt
+++ b/js/js.translator/testData/box/expression/try/exceptionToString.kt
@@ -1,3 +1,4 @@
+// IGNORE_BACKEND: JS
 // EXPECTED_REACHABLE_NODES: 1298
 package foo
 
@@ -8,8 +9,10 @@ class MyException3: Throwable {
     constructor(m: String? = null) : super(m) {}
 }
 
-// TODO: add direct inheritors of Throwable:
-// - with cause only, in the primary constructor
+class MyException4(c: Throwable? = null): Throwable(c)
+class MyException5: Throwable {
+    constructor(c: Throwable? = null) : super(c) {}
+}
 
 fun check(e: Throwable, expectedString: String) {
     try {
@@ -21,22 +24,28 @@ fun check(e: Throwable, expectedString: String) {
 }
 
 fun box(): String {
-    check(Throwable(), "Throwable: null")
+    check(Throwable(), "Throwable")
     check(Throwable("ccc"), "Throwable: ccc")
     check(Throwable(Throwable("ddd")), "Throwable: Throwable: ddd")
-    check(Exception(), "Exception: null")
+    check(Exception(), "Exception")
     check(Exception("bbb"), "Exception: bbb")
     check(Exception(Exception("ccc")), "Exception: Exception: ccc")
-    check(AssertionError(), "AssertionError: null")
-    check(AssertionError(null), "AssertionError: null")
+    check(AssertionError(), "AssertionError")
+    check(AssertionError(null), "AssertionError")
     check(AssertionError("bbb"), "AssertionError: bbb")
     check(AssertionError(Exception("ccc")), "AssertionError: Exception: ccc")
-    check(MyException(), "MyException: null")
+    check(MyException(), "MyException")
     check(MyException("aaa"), "MyException: aaa")
-    check(MyException2(), "MyException2: null")
+    check(MyException2(), "MyException2")
     check(MyException2("aaa"), "MyException2: aaa")
-    check(MyException3(), "MyException3: null")
+    check(MyException3(), "MyException3")
     check(MyException3("aaa"), "MyException3: aaa")
 
+    check(MyException4(), "MyException4")
+    check(MyException4(AssertionError()), "MyException4: AssertionError")
+
+    check(MyException5(), "MyException5")
+    check(MyException5(MyException5()), "MyException5: MyException5")
+
     return "OK"
 }
diff --git a/js/js.translator/testData/box/expression/try/exceptionToString_legacy.kt b/js/js.translator/testData/box/expression/try/exceptionToString_legacy.kt
new file mode 100644
index 00000000000..299f334f2e1
--- /dev/null
+++ b/js/js.translator/testData/box/expression/try/exceptionToString_legacy.kt
@@ -0,0 +1,51 @@
+// DONT_TARGET_EXACT_BACKEND: JS_IR
+// EXPECTED_REACHABLE_NODES: 1298
+package foo
+
+class MyException(m: String? = null): Exception(m)
+class MyException2(m: String? = null): Throwable(m)
+
+class MyException3: Throwable {
+    constructor(m: String? = null) : super(m) {}
+}
+
+class MyException4(c: Throwable? = null): Throwable(c)
+class MyException5: Throwable {
+    constructor(c: Throwable? = null) : super(c) {}
+}
+
+fun check(e: Throwable, expectedString: String) {
+    try {
+        throw e
+    }
+    catch (e: Throwable) {
+        assertEquals(expectedString, e.toString())
+    }
+}
+
+fun box(): String {
+    check(Throwable(), "Throwable: null")
+    check(Throwable("ccc"), "Throwable: ccc")
+    check(Throwable(Throwable("ddd")), "Throwable: Throwable: ddd")
+    check(Exception(), "Exception: null")
+    check(Exception("bbb"), "Exception: bbb")
+    check(Exception(Exception("ccc")), "Exception: Exception: ccc")
+    check(AssertionError(), "AssertionError: null")
+    check(AssertionError(null), "AssertionError: null")
+    check(AssertionError("bbb"), "AssertionError: bbb")
+    check(AssertionError(Exception("ccc")), "AssertionError: Exception: ccc")
+    check(MyException(), "MyException: null")
+    check(MyException("aaa"), "MyException: aaa")
+    check(MyException2(), "MyException2: null")
+    check(MyException2("aaa"), "MyException2: aaa")
+    check(MyException3(), "MyException3: null")
+    check(MyException3("aaa"), "MyException3: aaa")
+
+    check(MyException4(), "MyException4")
+    check(MyException4(AssertionError()), "MyException4: AssertionError: null")
+
+    check(MyException5(), "MyException5")
+    check(MyException5(MyException5()), "MyException5: MyException5")
+
+    return "OK"
+}
diff --git a/libraries/stdlib/js-ir/runtime/coreRuntime.kt b/libraries/stdlib/js-ir/runtime/coreRuntime.kt
index 3c99ecbaea9..1e091cf010a 100644
--- a/libraries/stdlib/js-ir/runtime/coreRuntime.kt
+++ b/libraries/stdlib/js-ir/runtime/coreRuntime.kt
@@ -87,7 +87,7 @@ internal fun captureStack(instance: Throwable) {
 
 internal fun newThrowable(message: String?, cause: Throwable?): Throwable {
     val throwable = js("new Error()")
-    throwable.message = message ?: cause?.toString()
+    throwable.message = message ?: cause?.toString() ?: undefined
     throwable.cause = cause
     throwable.name = "Throwable"
     return throwable.unsafeCast<Throwable>()
@@ -95,7 +95,7 @@ internal fun newThrowable(message: String?, cause: Throwable?): Throwable {
 
 internal fun extendThrowable(this_: dynamic, message: String?, cause: Throwable?) {
     js("Error").call(this_)
-    this_.message = message ?: cause?.toString()
+    this_.message = message ?: cause?.toString() ?: undefined
     this_.cause = cause
     captureStack(this_)
 }