diff --git a/src/serialize.h b/src/serialize.h
index cb3a3ea0..857d0468 100644
--- a/src/serialize.h
+++ b/src/serialize.h
@@ -30,6 +30,7 @@ typedef unsigned long long  uint64;
 #endif
 
 #ifdef __WXMSW__
+#include <windows.h>
 // This is used to attempt to keep keying material out of swap
 // Note that VirtualLock does not provide this as a guarantee on Windows,
 // but, in practice, memory that has been VirtualLock'd almost never gets written to