diff --git a/hotp/host/main.c b/hotp/host/main.c
index 2758312..a8071bf 100644
--- a/hotp/host/main.c
+++ b/hotp/host/main.c
@@ -44,7 +44,7 @@
 	TEEC_Session sess;
 	TEEC_UUID uuid = TA_HOTP_UUID;
 
-	int i;
+	size_t i;
 	uint32_t err_origin;
 	uint32_t hotp_value;