Fix.

library/src/main/java/com/afollestad/materialdialogs/MaterialDialog.java

@@ -184,6 +184,7 @@ public class MaterialDialog extends DialogBase implements View.OnClickListener,
         boolean adapterProvided = adapter != null;
         if (items != null && items.length > 0 || adapterProvided) {
             title = (TextView) view.findViewById(R.id.titleCustomView);
+            icon = (ImageView) view.findViewById(R.id.iconCustomView);
             listView = (ListView) view.findViewById(R.id.contentListView);
             listView.setSelector(DialogUtils.resolveDrawable(getContext(), R.attr.md_selector));
             ((MeasureCallbackListView) listView).setCallback(this);