diff --git a/src/disk/hdc_st506_xt.c b/src/disk/hdc_st506_xt.c
index f3ac48a36..ab4b10b78 100644
--- a/src/disk/hdc_st506_xt.c
+++ b/src/disk/hdc_st506_xt.c
@@ -1702,7 +1702,7 @@ st506_init(const device_t *info)
             dev->base     = device_get_config_hex16("base");
             dev->irq      = device_get_config_int("irq");
             if (dev->irq == 2)
-                dev->switches |= 0x40;
+                dev->switches |= 0x80;
             dev->bios_addr = device_get_config_hex20("bios_addr");
             break;
 
@@ -1732,7 +1732,7 @@ st506_init(const device_t *info)
             dev->base     = device_get_config_hex16("base");
             dev->irq      = device_get_config_int("irq");
             if (dev->irq == 2)
-                dev->switches |= 0x40;
+                dev->switches |= 0x80;
             dev->bios_addr = device_get_config_hex20("bios_addr");
             break;
 
@@ -1747,7 +1747,7 @@ st506_init(const device_t *info)
             dev->base     = device_get_config_hex16("base");
             dev->irq      = device_get_config_int("irq");
             if (dev->irq == 2)
-                dev->switches |= 0x40;
+                dev->switches |= 0x80;
             dev->bios_addr = device_get_config_hex20("bios_addr");
             break;