diff --git a/drivers/staging/greybus/tools/loopback_test.c b/drivers/staging/greybus/tools/loopback_test.c
index f7f4cd6fb55b..9430f3e0162b 100644
--- a/drivers/staging/greybus/tools/loopback_test.c
+++ b/drivers/staging/greybus/tools/loopback_test.c
@@ -646,7 +646,7 @@ baddir:
 static int open_poll_files(struct loopback_test *t)
 {
 	struct loopback_device *dev;
-	char buf[MAX_STR_LEN];
+	char buf[MAX_SYSFS_PATH + MAX_STR_LEN];
 	char dummy;
 	int fds_idx = 0;
 	int i;