diff --git a/tools/testing/selftests/damon/huge_count_read_write.c b/tools/testing/selftests/damon/huge_count_read_write.c
index a6fe0689f88d..f3c199dc8eba 100644
--- a/tools/testing/selftests/damon/huge_count_read_write.c
+++ b/tools/testing/selftests/damon/huge_count_read_write.c
@@ -18,7 +18,7 @@
 void write_read_with_huge_count(char *file)
 {
 	int filedesc = open(file, O_RDWR);
-	char buf[25];
+	char buf[256];
 	int ret;
 
 	printf("%s %s\n", __func__, file);