diff --git a/src/lib/src/fwts_battery.c b/src/lib/src/fwts_battery.c
index 94084c0..008951d 100644
--- a/src/lib/src/fwts_battery.c
+++ b/src/lib/src/fwts_battery.c
@@ -38,8 +38,8 @@ static int fwts_battery_get_capacity_sys_fs(fwts_framework *fw,
 	struct dirent *entry;
 	char *field_mAh;
 	char *field_mWh;
-	int  field_mAh_len;
-	int  field_mWh_len;
+	size_t field_mAh_len;
+	size_t field_mWh_len;
 	int  i = 0;
 
 	switch (type) {