Index: uspace/drv/audio/sb16/dsp.c
===================================================================
--- uspace/drv/audio/sb16/dsp.c	(revision fb6c98fec617c3dbf8d6c2b59023fb17187fbc23)
+++ uspace/drv/audio/sb16/dsp.c	(revision 6f57933d436aab277502e3607a1403c7b37f051f)
@@ -322,5 +322,5 @@
 {
 	assert(dsp);
-	if (dsp->event_session)
+	if (dsp->event_session && session)
 		return EBUSY;
 	dsp->event_session = session;