diff --git a/tools/testing/selftests/vm/split_huge_page_test.c b/tools/testing/selftests/vm/split_huge_page_test.c
index 1af16d2c2a0acb5ea27b7e5e8f8dc864c27a416f..52497b7b9f1db3e7203ea476b03b19b5e643b763 100644
--- a/tools/testing/selftests/vm/split_huge_page_test.c
+++ b/tools/testing/selftests/vm/split_huge_page_test.c
@@ -341,7 +341,7 @@ void split_file_backed_thp(void)
 	}
 
 	/* write something to the file, so a file-backed THP can be allocated */
-	num_written = write(fd, tmpfs_loc, sizeof(tmpfs_loc));
+	num_written = write(fd, tmpfs_loc, strlen(tmpfs_loc) + 1);
 	close(fd);
 
 	if (num_written < 1) {