diff --git a/src/sound_sb_dsp.c b/src/sound_sb_dsp.c
index fb4c153..0300c24 100644
--- a/src/sound_sb_dsp.c
+++ b/src/sound_sb_dsp.c
@@ -734,11 +734,11 @@ uint8_t sb_read(uint16_t a, void *priv)
 //                pclog("SB read %02X\n",sbreaddat);
                 return dsp->sbreaddat;
                 case 0xC: /*Write data ready*/
-                if (dsp->sb_8_enable || dsp->sb_type >= SB16 )
-                        dsp->busy_count = (dsp->busy_count + 1) & 15;
+                if (dsp->sb_8_enable || dsp->sb_type >= SB16)
+                        dsp->busy_count = (dsp->busy_count + 1) & 3;
                 else
                         dsp->busy_count = 0;
-                if (dsp->wb_full || (dsp->busy_count & 8))
+                if (dsp->wb_full || (dsp->busy_count & 2))
                 {
                         dsp->wb_full = dsp->wb_time;
                         return 0xff;