diff --git a/drivers/mmc/rpmb.c b/drivers/mmc/rpmb.c
index 1c6888f..0b6b622 100644
--- a/drivers/mmc/rpmb.c
+++ b/drivers/mmc/rpmb.c
@@ -67,7 +67,7 @@ struct s_rpmb {
 	unsigned char mac[RPMB_SZ_MAC];
 	unsigned char data[RPMB_SZ_DATA];
 	unsigned char nonce[RPMB_SZ_NONCE];
-	unsigned long write_counter;
+	unsigned int write_counter;
 	unsigned short address;
 	unsigned short block_count;
 	unsigned short result;