diff --git a/src/borg/hashindex.pyx b/src/borg/hashindex.pyx
index 53ebcf804..0e0ecc913 100644
--- a/src/borg/hashindex.pyx
+++ b/src/borg/hashindex.pyx
@@ -129,6 +129,7 @@ cdef class IndexBase:
     def setdefault(self, key, value):
         if not key in self:
             self[key] = value
+        return self[key]
 
     def __delitem__(self, key):
         assert len(key) == self.key_size
diff --git a/src/borg/testsuite/hashindex.py b/src/borg/testsuite/hashindex.py
index 5fac6f6c4..764de1147 100644
--- a/src/borg/testsuite/hashindex.py
+++ b/src/borg/testsuite/hashindex.py
@@ -70,6 +70,21 @@ class HashIndexTestCase(BaseTestCase):
             idx.write(filepath)
             del idx
             self.assert_equal(len(cls.read(filepath)), 0)
+        idx = cls()
+        # Test setdefault - set non-existing key
+        idx.setdefault(H(0), make_value(42))
+        assert H(0) in idx
+        assert idx[H(0)] == make_value(42)
+        # Test setdefault - do not set existing key
+        idx.setdefault(H(0), make_value(23))
+        assert H(0) in idx
+        assert idx[H(0)] == make_value(42)
+        # Test setdefault - get-like return value, key not present
+        assert idx.setdefault(H(1), make_value(23)) == make_value(23)
+        # Test setdefault - get-like return value, key present
+        assert idx.setdefault(H(0), make_value(23)) == make_value(42)
+        # clean up setdefault test
+        del idx
 
     def test_nsindex(self):
         self._generic_test(NSIndex, lambda x: (x, x),