diff --git a/js/js.libraries/src/core/javautil.kt b/js/js.libraries/src/core/javautil.kt
index 0ebca43e04f..c32deedf57f 100644
--- a/js/js.libraries/src/core/javautil.kt
+++ b/js/js.libraries/src/core/javautil.kt
@@ -74,7 +74,7 @@ public abstract class AbstractList<E>() : AbstractCollection<E>(), MutableList<E
 
     override fun subList(fromIndex: Int, toIndex: Int): MutableList<E> = noImpl
 
-    override val size: Int get() = noImpl
+    abstract override val size: Int
 
     override fun equals(other: Any?): Boolean = noImpl