diff --git a/include/wx/html/helpfrm.h b/include/wx/html/helpfrm.h
index ca8415ab25..8ab577fee1 100644
--- a/include/wx/html/helpfrm.h
+++ b/include/wx/html/helpfrm.h
@@ -70,7 +70,7 @@ struct wxHtmlHelpFrameCfg
     bool navig_on;
 };
 
-class wxHtmlHelpMergedIndexItem;
+struct wxHtmlHelpMergedIndexItem;
 class wxHtmlHelpMergedIndex;
 
 class WXDLLIMPEXP_CORE wxHelpControllerBase;