diff --git a/flang/lib/Parser/message.cpp b/flang/lib/Parser/message.cpp
--- a/flang/lib/Parser/message.cpp
+++ b/flang/lib/Parser/message.cpp
@@ -28,6 +28,10 @@
   return o;
 }
 
+#ifdef _MSC_VER
+#define vsnprintf _vsprintf_p
+#endif
+
 void MessageFormattedText::Format(const MessageFixedText *text, ...) {
   const char *p{text->text().begin()};
   std::string asString;