diff --git a/sys/dev/ct/ct.c b/sys/dev/ct/ct.c
index 71d62f52186b..f2fe883a7a32 100644
--- a/sys/dev/ct/ct.c
+++ b/sys/dev/ct/ct.c
@@ -229,7 +229,7 @@ cthw_chip_reset(bst, bsh, chipclk, hostid)
 
 	case 20:
 		seltout = (seltout * chipclk) / 20;
-		regv = IDR_FS_15_20;
+		regv = IDR_FS_16_20;
 		break;
 
 	default:
diff --git a/sys/i386/isa/bs/bsfunc.c b/sys/i386/isa/bs/bsfunc.c
index c0e5540f738e..b23a241d9638 100644
--- a/sys/i386/isa/bs/bsfunc.c
+++ b/sys/i386/isa/bs/bsfunc.c
@@ -780,7 +780,7 @@ bs_setup_ctrl(ti, quirks, flags)
 	period = BS_SCSI_PERIOD(flags);
 	offset = (flags & BS_SCSI_SYNC) ? BS_SCSI_OFFSET(flags) : 0;
 
-	maxperiod = (bsc->sc_cspeed & IDR_FS_15_20) ? 100 : 50;
+	maxperiod = (bsc->sc_cspeed & IDR_FS_16_20) ? 100 : 50;
 	if (period > maxperiod)
 		period = maxperiod;
 
diff --git a/sys/i386/isa/bs/bshw.c b/sys/i386/isa/bs/bshw.c
index fd7926004793..f60b229e34dc 100644
--- a/sys/i386/isa/bs/bshw.c
+++ b/sys/i386/isa/bs/bshw.c
@@ -286,17 +286,17 @@ bshw_board_probe(bsc, drq, irq)
 		break;
 
 	case 1:
-		bsc->sc_cspeed &= ~(IDR_FS_12_15 | IDR_FS_15_20);
+		bsc->sc_cspeed &= ~(IDR_FS_12_15 | IDR_FS_16_20);
 		break;
 
 	case 2:
-		bsc->sc_cspeed &= ~(IDR_FS_12_15 | IDR_FS_15_20);
+		bsc->sc_cspeed &= ~(IDR_FS_12_15 | IDR_FS_16_20);
 		bsc->sc_cspeed |= IDR_FS_12_15;
 		break;
 
 	case 3:
-		bsc->sc_cspeed &= ~(IDR_FS_12_15 | IDR_FS_15_20);
-		bsc->sc_cspeed |= IDR_FS_15_20;
+		bsc->sc_cspeed &= ~(IDR_FS_12_15 | IDR_FS_16_20);
+		bsc->sc_cspeed |= IDR_FS_16_20;
 		break;
 	}