diff --git a/drivers/mmc/mmc.c b/drivers/mmc/mmc.c
index f07505f556401cfd6a07c2cc83999b0edbacb57c..be211016cf5df42e95e8365ae5a8ccdde61889d2 100644
--- a/drivers/mmc/mmc.c
+++ b/drivers/mmc/mmc.c
@@ -1068,8 +1068,7 @@ static int mmc_startup(struct mmc *mmc)
 
 			/* Read out group size from ext_csd */
 			mmc->erase_grp_size =
-				ext_csd[EXT_CSD_HC_ERASE_GRP_SIZE] *
-					MMC_MAX_BLOCK_LEN * 1024;
+				ext_csd[EXT_CSD_HC_ERASE_GRP_SIZE] * 1024;
 			/*
 			 * if high capacity and partition setting completed
 			 * SEC_COUNT is valid even if it is smaller than 2 GiB
diff --git a/include/mmc.h b/include/mmc.h
index 18155c9d6cd5774321ddc2cf3a209276407add0f..6c8bbfc952b4184349010c29a9391cc7c204bcb8 100644
--- a/include/mmc.h
+++ b/include/mmc.h
@@ -315,7 +315,7 @@ struct mmc {
 	uint tran_speed;
 	uint read_bl_len;
 	uint write_bl_len;
-	uint erase_grp_size;
+	uint erase_grp_size;	/* in 512-byte sectors */
 	u64 capacity;
 	u64 capacity_user;
 	u64 capacity_boot;