diff --git a/tools/lib/api/fs/fs.c b/tools/lib/api/fs/fs.c
index edec23406dbc..3cc302d4c47b 100644
--- a/tools/lib/api/fs/fs.c
+++ b/tools/lib/api/fs/fs.c
@@ -294,11 +294,14 @@ int filename__read_int(const char *filename, int *value)
 {
 	char line[64];
 	int fd = open(filename, O_RDONLY), err = -1;
+	ssize_t n;
 
 	if (fd < 0)
 		return -errno;
 
-	if (read(fd, line, sizeof(line)) > 0) {
+	n = read(fd, line, sizeof(line) - 1);
+	if (n > 0) {
+		line[n] = '\0';
 		*value = atoi(line);
 		err = 0;
 	}
@@ -312,11 +315,14 @@ static int filename__read_ull_base(const char *filename,
 {
 	char line[64];
 	int fd = open(filename, O_RDONLY), err = -1;
+	ssize_t n;
 
 	if (fd < 0)
 		return -errno;
 
-	if (read(fd, line, sizeof(line)) > 0) {
+	n = read(fd, line, sizeof(line) - 1);
+	if (n > 0) {
+		line[n] = '\0';
 		*value = strtoull(line, NULL, base);
 		if (*value != ULLONG_MAX)
 			err = 0;