--- a/sys/mediafoundation/gstmfdevice.h
+++ b/sys/mediafoundation/gstmfdevice.h
@@ -31,9 +31,6 @@
 G_DECLARE_FINAL_TYPE (GstMFDeviceProvider,
     gst_mf_device_provider, GST, MF_DEVICE_PROVIDER, GstDeviceProvider);
 
-G_DEFINE_AUTOPTR_CLEANUP_FUNC(GstMFDevice, gst_object_unref)
-G_DEFINE_AUTOPTR_CLEANUP_FUNC(GstMFDeviceProvider, gst_object_unref)
-
 G_END_DECLS
 
 #endif /* __GST_MF_DEVICE_H__ */
\ No newline at end of file
--- a/sys/mediafoundation/gstmfutils.h
+++ b/sys/mediafoundation/gstmfutils.h
@@ -38,6 +38,10 @@
 
 G_BEGIN_DECLS
 
+#ifndef GUID_NULL
+DEFINE_GUID(GUID_NULL, 0,0,0, 0,0,0,0, 0,0,0,0);
+#endif
+
 #define GST_MF_VIDEO_FORMATS \
   "{ BGRx, BGRA, BGR, RGB15, RGB16, VUYA, YUY2, YVYU, UYVY, NV12, YV12, I420," \
   " P010, P016, v210, v216, GRAY16_LE }"
--- a/sys/mediafoundation/meson.build
+++ b/sys/mediafoundation/meson.build
@@ -44,9 +44,9 @@
   subdir_done()
 endif
 
-if cc.get_id() != 'msvc'
+if host_system != 'windows'
   if mf_option.enabled()
-    error('mediafoundation plugin can only be built with MSVC')
+    error('mediafoundation plugin can only be built for Microsoft Windows')
   endif
   subdir_done()
 endif
