diff --git a/vermouth/pdb/pdb.py b/vermouth/pdb/pdb.py
index 715a3ac56..4963ce938 100644
--- a/vermouth/pdb/pdb.py
+++ b/vermouth/pdb/pdb.py
@@ -344,7 +344,7 @@ def _finish_molecule(self, line="", lineno=0):
             if {"a", "b", "c"}.issubset(set(self.cryst.keys())):
                 self.active_molecule.box = np.array([self.cryst['a']/10.,
                                                      self.cryst['b']/10.,
-                                                     self.cryst['b']/10.])
+                                                     self.cryst['c']/10.])
             self.molecules.append(self.active_molecule)
         self.active_molecule = Molecule()
 
diff --git a/vermouth/tests/pdb/test_read_pdb.py b/vermouth/tests/pdb/test_read_pdb.py
index 86e6c844f..a651f15af 100644
--- a/vermouth/tests/pdb/test_read_pdb.py
+++ b/vermouth/tests/pdb/test_read_pdb.py
@@ -236,31 +236,31 @@ def test_atom_attributes():
 
 @pytest.mark.parametrize('pdbstr, cryst_dict', (
     # complete directive
-    ('''CRYST1   77.987   77.987   77.987  90.00  90.00  90.00 P 1           1
+    ('''CRYST1   77.987   87.987   97.987  90.00  90.00  90.00 P 1           1
     MODEL        1
     ATOM      1  EO  PEO     0      74.550  37.470  22.790  1.00  0.00
     ATOM      2  EO  PEO     1      77.020  38.150  25.000  1.00  0.00
     ATOM      3  EO  PEO     2      76.390  37.180  28.130  1.00  0.00
     ATOM      4  EO  PEO     3      75.430  37.920  31.450  1.00  0.00
     ''',
-    {"a": 77.987, "b": 77.987, "c": 77.987,
+    {"a": 77.987, "b": 87.987, "c": 97.987,
      "alpha": 90.0, "beta": 90.0, "gamma": 90,
     "space_group": "P 1", "z_value": 1}
     ),
     # incomplete directive
-    ('''CRYST1   77.987   77.987   77.987
+    ('''CRYST1   77.987   87.987   97.987
     MODEL        1
     ATOM      1  EO  PEO     0      74.550  37.470  22.790  1.00  0.00
     ATOM      2  EO  PEO     1      77.020  38.150  25.000  1.00  0.00
     ATOM      3  EO  PEO     2      76.390  37.180  28.130  1.00  0.00
     ATOM      4  EO  PEO     3      75.430  37.920  31.450  1.00  0.00
     ''',
-    {"a": 77.987, "b": 77.987, "c": 77.987,}
+    {"a": 77.987, "b": 87.987, "c": 97.987,}
     )))
 def test_cryst1(caplog, pdbstr, cryst_dict):
     parser = PDBParser()
     mols = list(parser.parse(pdbstr.splitlines()))
-    assert np.all(np.isclose(mols[0].box, np.array([7.7987, 7.7987, 7.7987])))
+    assert np.all(np.isclose(mols[0].box, np.array([7.7987, 8.7987, 9.7987])))
     assert parser.cryst == cryst_dict
     if len(cryst_dict) < 8:
         assert any(rec.levelname == 'WARNING' for rec in caplog.records)