diff --git a/tests/test_file_helper.cpp b/tests/test_file_helper.cpp
index 061f125f..8cd2fd77 100644
--- a/tests/test_file_helper.cpp
+++ b/tests/test_file_helper.cpp
@@ -44,7 +44,7 @@ TEST_CASE("file_helper_reopen", "[file_helper::reopen()]]")
     file_helper helper;
     helper.open(target_filename);
     write_with_helper(helper, 12);
-    REQUIRE(helper.size() == 12);
+    REQUIRE(helper.size() == 13);
     helper.reopen(true);
     REQUIRE(helper.size() == 0);
 }