diff --git a/Lib/test/test_capi/test_bytes.py b/Lib/test/test_capi/test_bytes.py
index c692ee82d04283..f0326c760c9db0 100644
--- a/Lib/test/test_capi/test_bytes.py
+++ b/Lib/test/test_capi/test_bytes.py
@@ -92,6 +92,7 @@ def test_size(self):
         # Test PyBytes_Size()
         size = _testcapi.bytes_size
 
+        self.assertEqual(size(b''), 0)
         self.assertEqual(size(b'abc'), 3)
         self.assertEqual(size(BytesSubclass(b'abc')), 3)
         self.assertRaises(TypeError, size, bytearray(b'abc'))