diff --git a/extensions/cpp/package.json b/extensions/cpp/package.json
index 78eb36d7e82..0e12733535f 100644
--- a/extensions/cpp/package.json
+++ b/extensions/cpp/package.json
@@ -41,6 +41,7 @@
           ".ino",
           ".inl",
           ".ipp",
+          ".ixx",
           ".hpp.in",
           ".h.in"
         ],