src/jdk.scripting.nashorn/share/classes/jdk/nashorn/internal/objects/NativeInt8Array.java

@@ -111,18 +111,17 @@
             }
         }
 
         private void setElem(final int index, final int elem) {
             try {
-                nb.put(index, (byte)elem);
+                if (index < nb.limit()) {
+                    nb.put(index, (byte) elem);
+                }
             } catch (final IndexOutOfBoundsException e) {
-                //swallow valid array indexes. it's ok.
-                if (index < 0) {
                     throw new ClassCastException();
                 }
             }
-        }
 
         @Override
         public int getInt(final int index) {
             return getElem(index);
         }