diff --git a/source/snd_oss.c b/source/snd_oss.c
index 9c3f349..ab16935 100644
--- a/source/snd_oss.c
+++ b/source/snd_oss.c
@@ -146,8 +146,8 @@ qboolean SNDDMA_Init(void)
 // memory map the dma buffer
 
 	shm->buffer = (unsigned char *) mmap(NULL, info.fragstotal
-		* info.fragsize, PROT_WRITE, MAP_FILE|MAP_SHARED, audio_fd, 0);
-	if (!shm->buffer || shm->buffer == (unsigned char *)-1)
+		* info.fragsize, PROT_READ|PROT_WRITE, MAP_FILE|MAP_SHARED, audio_fd, 0);
+	if (!shm->buffer || shm->buffer == MAP_FAILED)
 	{
 		perror("/dev/dsp");
 		Con_Printf("Could not mmap /dev/dsp\n");