diff --git a/src/pinnable_mapped_file.cpp b/src/pinnable_mapped_file.cpp
index a78cc6a..06a2ea1 100644
--- a/src/pinnable_mapped_file.cpp
+++ b/src/pinnable_mapped_file.cpp
@@ -224,7 +224,7 @@ pinnable_mapped_file::pinnable_mapped_file(const std::filesystem::path& dir, boo
    }
    std::byte* start = (std::byte*)_segment_manager;
    assert(_segment_manager_map.find(start) == _segment_manager_map.end());
-   _segment_manager_map[start] = start + _database_size;
+   _segment_manager_map[start] = start + _segment_manager->get_size();
 }
 
 void pinnable_mapped_file::setup_copy_on_write_mapping() {