diff --git a/drivers/mmc/mmc.c b/drivers/mmc/mmc.c
index 31f65f6..c930893 100644
--- a/drivers/mmc/mmc.c
+++ b/drivers/mmc/mmc.c
@@ -1969,7 +1969,7 @@
 		return -ENOMEM;
 	memcpy(mmc->ext_csd, ext_csd, MMC_MAX_BLOCK_LEN);
 
-	if (ext_csd[EXT_CSD_REV] > ARRAY_SIZE(mmc_versions))
+	if (ext_csd[EXT_CSD_REV] >= ARRAY_SIZE(mmc_versions))
 		return -EINVAL;
 
 	mmc->version = mmc_versions[ext_csd[EXT_CSD_REV]];