diff --git a/hw/audio/sb16.c b/hw/audio/sb16.c
index bda26d0123b81c60201bfb7d96fbeac431e34a6b..444eb9e419f1babb75c831faca0d3ebfe9a6672d 100644
--- a/hw/audio/sb16.c
+++ b/hw/audio/sb16.c
@@ -999,7 +999,7 @@ static IO_READ_PROTO (dsp_read)
         retval = (!s->out_data_len || s->highspeed) ? 0 : 0x80;
         if (s->mixer_regs[0x82] & 1) {
             ack = 1;
-            s->mixer_regs[0x82] &= 1;
+            s->mixer_regs[0x82] &= ~1;
             qemu_irq_lower (s->pic);
         }
         break;
@@ -1008,7 +1008,7 @@ static IO_READ_PROTO (dsp_read)
         retval = 0xff;
         if (s->mixer_regs[0x82] & 2) {
             ack = 1;
-            s->mixer_regs[0x82] &= 2;
+            s->mixer_regs[0x82] &= ~2;
             qemu_irq_lower (s->pic);
         }
         break;