diff --git a/reactos/dll/win32/cryptui/main.c b/reactos/dll/win32/cryptui/main.c
index a95a7a487d3..43daba7287c 100644
--- a/reactos/dll/win32/cryptui/main.c
+++ b/reactos/dll/win32/cryptui/main.c
@@ -27,6 +27,7 @@
 #include "winbase.h"
 #include "winnls.h"
 #include "winuser.h"
+#include "undocuser.h"
 #include "softpub.h"
 #include "wingdi.h"
 #include "richedit.h"