diff --git a/CHANGES.rst b/CHANGES.rst
index 0b6cf37..f398448 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -13,6 +13,7 @@ Version 0.10
 **Changes:**
 
 - Fixed GraceEffect.durationTime `#34 <https://github.com/Perlence/PyGuitarPro/issues/34>`_.
+- Fixed hashing `#31 <https://github.com/Perlence/PyGuitarPro/issues/31>`_.
 
 
 Version 0.9.2
diff --git a/guitarpro/models.py b/guitarpro/models.py
index 46f2903..74d64bb 100644
--- a/guitarpro/models.py
+++ b/guitarpro/models.py
@@ -45,6 +45,11 @@ def __eq__(self, other):
             return self._value_ == other._value_
         return super().__eq__(other)
 
+    def __hash__(self):
+        if self._name_ == 'unknown':
+            return hash(self._value_)
+        return hash(self._name_)
+
 
 def hashableAttrs(cls=None, repr=True):
     """A fully hashable attrs decorator.
@@ -1132,16 +1137,13 @@ class Chord:
     ninth: Optional['ChordAlteration'] = None
     eleventh: Optional['ChordAlteration'] = None
     firstFret: Optional[int] = None
-    strings: List[int] = attr.Factory(list)
+    strings: List[int] = attr.Factory(lambda self: [-1] * self.length, takes_self=True)
     barres: List['Barre'] = attr.Factory(list)
     omissions: List[bool] = attr.Factory(list)
     fingerings: List[Fingering] = attr.Factory(list)
     show: Optional[bool] = None
     newFormat: Optional[bool] = None
 
-    def __attrs_post_init__(self):
-        self.strings = [-1] * self.length
-
     @property
     def notes(self):
         return [string for string in self.strings if string >= 0]
diff --git a/tests/test_conversion.py b/tests/test_conversion.py
index 0026e90..af0bf51 100644
--- a/tests/test_conversion.py
+++ b/tests/test_conversion.py
@@ -56,6 +56,7 @@ def testReadWriteEquals(tmpdir, filename):
     gp.write(songA, destpath)
     songB = gp.parse(destpath)
     assert songA == songB
+    assert hash(songA) == hash(songB)
 
 
 @pytest.mark.parametrize('source, targetExt', CONVERSION_TESTS)