diff --git a/enumcom.c b/enumcom.c
index 29ca0d3..1009090 100644
--- a/enumcom.c
+++ b/enumcom.c
@@ -39,7 +39,9 @@
 #include <objbase.h>
 #include <setupapi.h>
 
+#ifndef GUID_DEVINTERFACE_COMPORT
 DEFINE_GUID(GUID_DEVINTERFACE_COMPORT, 0x86e0d1e0L, 0x8089, 0x11d0, 0x9c, 0xe4, 0x08, 0x00, 0x3e, 0x30, 0x1f, 0x73);
+#endif
 
 #ifdef MAIN
 int CheckPort(const char* port, void* data)