diff --git a/hwilib/serializations.py b/hwilib/serializations.py
index 21979e3..e76d5f2 100644
--- a/hwilib/serializations.py
+++ b/hwilib/serializations.py
@@ -612,7 +612,8 @@ class PartiallySignedInput:
 
         if not self.final_script_witness.is_null():
             r += ser_string(b"\x08")
-            r += self.final_script_witness.serialize()
+            witstack = self.final_script_witness.serialize()
+            r += ser_string(witstack)
 
         for key, value in sorted(self.unknown.items()):
             r += ser_string(key)
diff --git a/test/data/test_psbt.json b/test/data/test_psbt.json
index 4a3d47f..39dccdb 100644
--- a/test/data/test_psbt.json
+++ b/test/data/test_psbt.json
@@ -25,7 +25,8 @@
         "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",
         "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",
         "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",
-        "cHNidP8BAH0CAAAAAXTJ5KdKezIfJIIqamLIyQxivxrXhgf0hPJdvDIqZe6ZAAAAAAD/////AgDzKwQAAAAAIgAgOAAOiTkWbVRkLTkK6SJLaZ12Qg/sYIwNOSsiBsnDiXWAlpgAAAAAABYAFG/wUHGvbEs/3RQIpNhYdh/09gwmAAAAAE8BBDWHzwRj1QHLgAAAAmDUcFrNsZhPXsreojbjRfHxKRktQR/bg0UG9IFxkSkqA5dwhHV4cNGNLjhFGEjc/IvZYHqamzEDsDWj18pA3Ys9FPeeyRCAAAAwgAAAAYAAAACAAAACTwEENYfPBMAmm9aAAAACdEGWiAl3lI+b68dxXnedY+qqqBs7PJpP4u/AI1jBMB4De/ZrB9O5eDy4bBkjuYINiEa2E87TrKU1T7gCJcRPsQkUfBbvIIAAADCAAAABgAAAAIAAAAIAAQErpJfEBAAAAAAiACA4AA6JORZtVGQtOQrpIktpnXZCD+xgjA05KyIGycOJdQEFR1IhAsdc2uyHckrqUdmo8qRSAyeTIpeSBycQjK7AO6wCKSR/IQO947/flOxdVTqxIznQ6CBY/drvmcvQOSz5iJM1VR+5PlKuIgYCx1za7IdySupR2ajypFIDJ5Mil5IHJxCMrsA7rAIpJH8cfBbvIDAAAIABAACAAAAAgAIAAIABAAAAAAAAACIGA73jv9+U7F1VOrEjOdDoIFj92u+Zy9A5LPmIkzVVH7k+HPeeyRAwAACAAQAAgAAAAIACAACAAQAAAAAAAAAAAQFHUiECx1za7IdySupR2ajypFIDJ5Mil5IHJxCMrsA7rAIpJH8hA73jv9+U7F1VOrEjOdDoIFj92u+Zy9A5LPmIkzVVH7k+Uq4iAgLHXNrsh3JK6lHZqPKkUgMnkyKXkgcnEIyuwDusAikkfxx8Fu8gMAAAgAEAAIAAAACAAgAAgAEAAAAAAAAAIgIDveO/35TsXVU6sSM50OggWP3a75nL0Dks+YiTNVUfuT4c957JEDAAAIABAACAAAAAgAIAAIABAAAAAAAAAAAA"
+        "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",
+        "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"
     ],
     "creator" : [
         {
@@ -96,4 +97,4 @@
             "result" : "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"
         }
     ]
-}
\ No newline at end of file
+}