diff --git a/src/device/isapnp.c b/src/device/isapnp.c
index 18b11ba3d..45752a3ca 100644
--- a/src/device/isapnp.c
+++ b/src/device/isapnp.c
@@ -414,7 +414,7 @@ isapnp_write_addr(uint16_t addr, uint8_t val, void *priv)
 		if (!dev->key_pos) {
 			isapnp_log("ISAPnP: Key unlocked, putting cards to SLEEP\n");
 			while (card) {
-				if (card->enable && (card->state == PNP_STATE_WAIT_FOR_KEY))
+				if (card->enable && (card->enable != ISAPNP_CARD_NO_KEY) && (card->state == PNP_STATE_WAIT_FOR_KEY))
 					card->state = PNP_STATE_SLEEP;
 				card = card->next;
 			}
@@ -974,14 +974,12 @@ isapnp_enable_card(void *priv, uint8_t enable)
 
     /* Look for a matching card. */
     isapnp_card_t *card = dev->first_card;
-    uint8_t will_enable;
     while (card) {
 	if (card == priv) {
 		/* Enable or disable the card. */
-		will_enable = (enable >= ISAPNP_CARD_ENABLE);
-		if (will_enable ^ card->enable)
+		if (!!enable ^ !!card->enable)
 			card->state = (enable == ISAPNP_CARD_FORCE_CONFIG) ? PNP_STATE_CONFIG : PNP_STATE_WAIT_FOR_KEY;
-		card->enable = will_enable;
+		card->enable = enable;
 
 		/* Invalidate other references if we're disabling this card. */
 		if (!card->enable) {
diff --git a/src/include/86box/isapnp.h b/src/include/86box/isapnp.h
index 38fc59d07..87272d86a 100644
--- a/src/include/86box/isapnp.h
+++ b/src/include/86box/isapnp.h
@@ -28,7 +28,8 @@
 enum {
     ISAPNP_CARD_DISABLE = 0,
     ISAPNP_CARD_ENABLE = 1,
-    ISAPNP_CARD_FORCE_CONFIG /* cheat code for UMC UM8669F */
+    ISAPNP_CARD_FORCE_CONFIG, /* cheat code for UMC UM8669F */
+    ISAPNP_CARD_NO_KEY /* cheat code for Crystal CS423x */
 };
 
 
diff --git a/src/sound/snd_cs423x.c b/src/sound/snd_cs423x.c
index c1e19a630..fa0a5c13a 100644
--- a/src/sound/snd_cs423x.c
+++ b/src/sound/snd_cs423x.c
@@ -547,11 +547,8 @@ cs423x_pnp_enable(cs423x_t *dev, uint8_t update_rom, uint8_t update_hwconfig)
 	if (update_rom)
 		isapnp_update_card_rom(dev->pnp_card, &dev->ram_data[dev->pnp_offset], 384);
 
-	/* Hide PnP card if the PKD bit is set, or if PnP was disabled by command 0x55. */
-	if ((dev->ram_data[0x4002] & 0x20) || !dev->pnp_enable)
-		isapnp_enable_card(dev->pnp_card, ISAPNP_CARD_DISABLE);
-	else
-		isapnp_enable_card(dev->pnp_card, ISAPNP_CARD_ENABLE);
+	/* Disable PnP key if the PKD bit is set, or if it was disabled by command 0x55. */
+	isapnp_enable_card(dev->pnp_card, ((dev->ram_data[0x4002] & 0x20) || !dev->pnp_enable) ? ISAPNP_CARD_NO_KEY : ISAPNP_CARD_ENABLE);
     }
 
     /* Update some register bits based on the config data in RAM if requested. */