diff --git a/audio/audio.c b/audio/audio.c
index 5e2d4cfb0fcaf230c3aae60cd2ca56d53aa33cc0..20bb2fc264cd20d77cc2f16c7377b2e0b0b85f5a 100644
--- a/audio/audio.c
+++ b/audio/audio.c
@@ -205,7 +205,7 @@ static char *audio_alloc_prefix (const char *s)
     }
 
     len = strlen (s);
-    r = qemu_malloc (len + sizeof (qemu_prefix) + 1);
+    r = qemu_malloc (len + sizeof (qemu_prefix));
 
     if (r) {
         size_t i;