diff --git a/include/SDL_platform.h b/include/SDL_platform.h
index b3a8962ff..af084f245 100644
--- a/include/SDL_platform.h
+++ b/include/SDL_platform.h
@@ -22,6 +22,9 @@
 
 /* Try to get a standard set of platform defines */
 
+#ifndef _SDL_platform_h
+#define _SDL_platform_h
+
 #if defined(_AIX)
 #undef __AIX__
 #define __AIX__		1
@@ -102,3 +105,5 @@
 #undef __WIN32__
 #define __WIN32__	1
 #endif
+
+#endif /* _SDL_platform_h */
diff --git a/src/audio/SDL_audio.c b/src/audio/SDL_audio.c
index c7ccc8bd8..fbc61be6f 100644
--- a/src/audio/SDL_audio.c
+++ b/src/audio/SDL_audio.c
@@ -436,7 +436,7 @@ int SDL_OpenAudio(SDL_AudioSpec *desired, SDL_AudioSpec *obtained)
 	audio->enabled = 1;
 	audio->paused  = 1;
 
-#if SDL_AUDIO_DRIVER_AHI
+#if !SDL_AUDIO_DRIVER_AHI
 
 /* AmigaOS opens audio inside the main loop */
 	audio->opened = audio->OpenAudio(audio, &audio->spec)+1;
@@ -511,7 +511,7 @@ int SDL_OpenAudio(SDL_AudioSpec *desired, SDL_AudioSpec *obtained)
 		}
 	}
 
-#if SDL_AUDIO_DRIVER_AHI
+#if !SDL_AUDIO_DRIVER_AHI
 	/* Start the audio thread if necessary */
 	switch (audio->opened) {
 		case  1:
@@ -611,7 +611,7 @@ void SDL_AudioQuit(void)
 			SDL_FreeAudioMem(audio->convert.buf);
 
 		}
-#if SDL_AUDIO_DRIVER_AHI
+#if !SDL_AUDIO_DRIVER_AHI
 		if ( audio->opened ) {
 			audio->CloseAudio(audio);
 			audio->opened = 0;