diff --git a/src/tools/qdoc/cppcodemarker.cpp b/src/tools/qdoc/cppcodemarker.cpp
index 4e5a9eb500..20c3316457 100644
--- a/src/tools/qdoc/cppcodemarker.cpp
+++ b/src/tools/qdoc/cppcodemarker.cpp
@@ -87,6 +87,8 @@ bool CppCodeMarker::recognizeExtension(const QString& extension)
     return ext == "c" ||
             ext == "c++" ||
             ext == "qdoc" ||
+            ext == "qtt" ||
+            ext == "qtx" ||
             ext == "cc" ||
             ext == "cpp" ||
             ext == "cxx" ||