diff --git a/js/js.libraries/src/core/javalang.kt b/js/js.libraries/src/core/javalang.kt
index ecbf2ebead4..e98f2197228 100644
--- a/js/js.libraries/src/core/javalang.kt
+++ b/js/js.libraries/src/core/javalang.kt
@@ -4,25 +4,25 @@ import java.io.IOException
 import js.library
 
 library
-open public class Exception() : Throwable() {}
+open public class Exception(message: String? = null) : Throwable() {}
 
 library("splitString")
 public fun String.split(regex : String) : Array<String> = js.noImpl
 
 library
-public class IllegalArgumentException(message: String = "") : Exception() {}
+public class IllegalArgumentException(message: String? = null) : Exception() {}
 
 library
-public class IllegalStateException(message: String = "") : Exception() {}
+public class IllegalStateException(message: String? = null) : Exception() {}
 
 library
-public class IndexOutOfBoundsException(message: String = "") : Exception() {}
+public class IndexOutOfBoundsException(message: String? = null) : Exception() {}
 
 library
-public class UnsupportedOperationException(message: String = "") : Exception() {}
+public class UnsupportedOperationException(message: String? = null) : Exception() {}
 
 library
-public class NumberFormatException(message: String = "") : Exception() {}
+public class NumberFormatException(message: String? = null) : Exception() {}
 
 library
 public trait Runnable {