diff --git a/include/sd_card.h b/include/sd_card.h
index ec6d582..b58fd7c 100644
--- a/include/sd_card.h
+++ b/include/sd_card.h
@@ -42,4 +42,8 @@ extern void sd_card_init(void);
 //#define CT_SDC		(CT_SD1|CT_SD2)	/* SD */
 #define CT_BLOCK	0x08		/* Block addressing */
 
+/*  SD error code bits */
+#define SD_ERR_IDLE_STATE       0x01
+#define SD_ERR_ILLEGAL_CMD      0x04
+
 #endif /* _SD_CARD_H_ */
diff --git a/spi/mmc.c b/spi/mmc.c
index 8819b59..1f20ddd 100644
--- a/spi/mmc.c
+++ b/spi/mmc.c
@@ -424,7 +424,7 @@ DSTATUS disk_initialize(uint8_t drv)
                 while (MCF_SLT_SCNT(0) - target > 0)
                 {
                     res = send_cmd(ACMD41, 1UL << 30);	/* Wait for end of initialization with ACMD41(HCS) */
-                    if (res != 0xff)
+                    if ((res & SD_ERR_IDLE_STATE) == 0)
                         break;
                 }
                 debug_printf("res = %d\r\n", res);