diff --git a/src/sound/snd_sb.c b/src/sound/snd_sb.c
index 2c735ce43..666393475 100644
--- a/src/sound/snd_sb.c
+++ b/src/sound/snd_sb.c
@@ -1133,6 +1133,8 @@ sb_ct1745_mixer_read(uint16_t addr, void *priv)
                     ret |= 0x01;
                 break;
 
+            case 0x0c:    /* Sound Blaster Pro Input Filter. */
+
             case 0x49:    /* Undocumented register used by some Creative drivers. */
             case 0x4a:    /* Undocumented register used by some Creative drivers. */
             case 0x8c:    /* Undocumented register used by some Creative drivers. */