diff --git a/js/js.libraries/src/core/core.kt b/js/js.libraries/src/core/core.kt
index a6b03627bba3f476b8f55f4770c6ae6707822d52..989995df13644daa1c9d539ce4d9f344e4e49c2b 100644
--- a/js/js.libraries/src/core/core.kt
+++ b/js/js.libraries/src/core/core.kt
@@ -25,6 +25,8 @@ fun safeParseDouble(s : String) : Double? = js.noImpl
 library
 open class Exception() : Throwable() {}
 library
+open class RuntimeException() : Exception() {}
+library
 class NumberFormatException() : Exception() {}
 
 native
diff --git a/js/js.libraries/src/core/javautil.kt b/js/js.libraries/src/core/javautil.kt
index ab3f03808e9b01ced12967af8fcb0f35cc6247f7..81cf79bf8bd77e98b2da4ffbd04e68801f256a68 100644
--- a/js/js.libraries/src/core/javautil.kt
+++ b/js/js.libraries/src/core/javautil.kt
@@ -19,6 +19,7 @@ library
 public open class Iterator<T>() {
     open fun next() : T = js.noImpl
     open fun hasNext() : Boolean = js.noImpl
+    open fun remove() : Unit = js.noImpl
 }
 
 library
@@ -173,4 +174,8 @@ library
 public class StringBuilder() {
     public fun append(obj : Any) : StringBuilder = js.noImpl
     public fun toString() : String = js.noImpl
-}
\ No newline at end of file
+}
+
+library
+class NoSuchElementException() : Exception() {}
+