#undef interface before including alsa headers.

diff --git a/dlls/winmm/winealsa/alsa.h b/dlls/winmm/winealsa/alsa.h
index 944e75b..16c7eff 100644
--- a/dlls/winmm/winealsa/alsa.h
+++ b/dlls/winmm/winealsa/alsa.h
@@ -18,7 +18,9 @@
 #ifndef __WINE_CONFIG_H
 # error You must include config.h to use this header
 #endif
-
+#ifdef interface
+#undef interface
+#endif
 #ifdef HAVE_ALSA_ASOUNDLIB_H
 #include <alsa/asoundlib.h>
 #elif defined(HAVE_SYS_ASOUNDLIB_H)