diff --git a/core/vul/vul_temp_filename.cxx b/core/vul/vul_temp_filename.cxx
index 87649e8..1fb263a 100644
--- a/core/vul/vul_temp_filename.cxx
+++ b/core/vul/vul_temp_filename.cxx
@@ -11,7 +11,7 @@
 
 #if defined (_MSC_VER) || defined(__MINGW32__)
 
-# include <Windows.h>
+# include <windows.h>
 #else
 #if defined(unix) || defined(__unix) || defined(__unix__) || defined(__APPLE__)
   // Helper functions for Unix