diff --git a/3rdparty/flite_hts_engine/CMakeLists.txt b/3rdparty/flite_hts_engine/CMakeLists.txt
index 28f6f628c..eb34c7c58 100644
--- a/3rdparty/flite_hts_engine/CMakeLists.txt
+++ b/3rdparty/flite_hts_engine/CMakeLists.txt
@@ -64,6 +64,10 @@ else()
         flite/lang/usenglish/us_text.c
         flite/lang/usenglish/usenglish.c
     )
+
+    if (MSVC)
+        add_definitions( -DNO_UNION_INITIALIZATION )
+    endif ()
 endif()
 
 if (SYSTEM_HTS_ENGINE)