diff --git a/biobb_structure_utils/test/unitests/test_utils/test_str_check_add_hydrogens.py b/biobb_structure_utils/test/unitests/test_utils/test_str_check_add_hydrogens.py
index 6f17ffb..7d9a2db 100644
--- a/biobb_structure_utils/test/unitests/test_utils/test_str_check_add_hydrogens.py
+++ b/biobb_structure_utils/test/unitests/test_utils/test_str_check_add_hydrogens.py
@@ -14,4 +14,4 @@ def teardown_class(self):
     def test_str_check_add_hydrogens(self):
         str_check_add_hydrogens(properties=self.properties, **self.paths)
         assert fx.not_empty(self.paths['output_structure_path'])
-        assert fx.equal(self.paths['output_structure_path'], self.paths['reference_output_structure_path'], percent_tolerance=50)
+        assert fx.equal(self.paths['output_structure_path'], self.paths['reference_output_structure_path'], percent_tolerance=10)