diff --git a/test/functional/data/rpc_psbt.json b/test/functional/data/rpc_psbt.json
index abc09d523a8..9e8131dbeb2 100644
--- a/test/functional/data/rpc_psbt.json
+++ b/test/functional/data/rpc_psbt.json
@@ -239,13 +239,6 @@
                 "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"
             ],
             "result" : "cHNidP8BAJoCAAAAAljoeiG1ba8MI76OcHBFbDNvfLqlyHV5JPVFiHuyq911AAAAAAD/////g40EJ9DsZQpoqka7CwmK6kQiwHGyyng1Kgd5WdB86h0BAAAAAP////8CcKrwCAAAAAAWABTYXCtx0AYLCcmIauuBXlCZHdoSTQDh9QUAAAAAFgAUAK6pouXw+HaliN9VRuh0LR2HAI8AAAAAAAEAuwIAAAABqtc5MQGL0l+ErkALaISL4J23BurCrBgpi6vucatlb4sAAAAASEcwRAIgWPb8fGoz4bMVSNSByCbAFb0wE1qtQs1neQ2rZtKtJDsCIEoc7SYExnNbY5PltBaR3XiwDwxZQvufdRhW+qk4FX26Af7///8CgPD6AgAAAAAXqRQPuUY0IWlrgsgzryQceMF9295JNIfQ8gonAQAAABepFCnKdPigj4GZlCgYXJe12FLkBj9hh2UAAAAiAgKVg785rgpgl0etGZrd1jT6YQhVnWxc05tMIYPxq5bgf0cwRAIgdAGK1BgAl7hzMjwAFXILNoTMgSOJEEjn282bVa1nnJkCIHPTabdA4+tT3O+jOCPIBwUUylWn3ZVE8VfBZ5EyYRGMASICAtq2H/SaFNtqfQKwzR+7ePxLGDErW05U2uTbovv+9TbXRzBEAiBjGpif5zipKtAZhgIzEsGSFP4oArOeXLwaw2eIBsaSwwIgOdtsOHvSZ3Ft/bPU2NpQuOhdITMmunx9qqTAzkHrkiMBAQMEAQAAAAEER1IhApWDvzmuCmCXR60Zmt3WNPphCFWdbFzTm0whg/GrluB/IQLath/0mhTban0CsM0fu3j8SxgxK1tOVNrk26L7/vU211KuIgYClYO/Oa4KYJdHrRma3dY0+mEIVZ1sXNObTCGD8auW4H8Q2QxqTwAAAIAAAACAAAAAgCIGAtq2H/SaFNtqfQKwzR+7ePxLGDErW05U2uTbovv+9TbXENkMak8AAACAAAAAgAEAAIAAAQEgAMLrCwAAAAAXqRS39fr0Dj1ApaRZsds1NfK3L6kh6IciAgMIncEMesbbVPkTKa9hczPbOIzq0MIx9yM3nRuZAwsC3EcwRAIgYut6VWEHp8c/RaxKtaHd329wdfsSdZaafzg+//eEvLICIAwF27dHDb8vCFV901bHMlwe0wkT6ZbNOECUXbEiKNpfASICAjrdkE89bc9Z3bkGsN7iNSm3/7ntUOXoYVGSaGAiHw5zRzBEAiBl9FulmYtZon/+GnvtAWrx8fkNVLOqj3RQql9WolEDvQIgf3JHA60e25ZoCyhLVtT/y4j3+3Weq74IqjDym4UTg9IBAQMEAQAAAAEEIgAgjCNTFzdDtZXftKB7crqOQuN5fadOh/59nXSX47ICiQMBBUdSIQMIncEMesbbVPkTKa9hczPbOIzq0MIx9yM3nRuZAwsC3CECOt2QTz1tz1nduQaw3uI1Kbf/ue1Q5ehhUZJoYCIfDnNSriIGAjrdkE89bc9Z3bkGsN7iNSm3/7ntUOXoYVGSaGAiHw5zENkMak8AAACAAAAAgAMAAIAiBgMIncEMesbbVPkTKa9hczPbOIzq0MIx9yM3nRuZAwsC3BDZDGpPAAAAgAAAAIACAACAACICA6mkw39ZltOqJdusa1cK8GUDlEkpQkYLNUdT7Z7spYdxENkMak8AAACAAAAAgAQAAIAAIgICf2OZdX0u/1WhNq0CxoSxg4tlVuXxtrNCgqlLa1AFEJYQ2QxqTwAAAIAAAACABQAAgAA="
-        },
-        {
-            "combine" : [
-                "cHNidP8BAD8CAAAAAf//////////////////////////////////////////AAAAAAD/////AQAAAAAAAAAAA2oBAAAAAAAKDwECAwQFBgcICQ8BAgMEBQYHCAkKCwwNDg8ACg8BAgMEBQYHCAkPAQIDBAUGBwgJCgsMDQ4PAAoPAQIDBAUGBwgJDwECAwQFBgcICQoLDA0ODwA=",
-                "cHNidP8BAD8CAAAAAf//////////////////////////////////////////AAAAAAD/////AQAAAAAAAAAAA2oBAAAAAAAKDwECAwQFBgcIEA8BAgMEBQYHCAkKCwwNDg8ACg8BAgMEBQYHCBAPAQIDBAUGBwgJCgsMDQ4PAAoPAQIDBAUGBwgQDwECAwQFBgcICQoLDA0ODwA="
-            ],
-            "result" : "cHNidP8BAD8CAAAAAf//////////////////////////////////////////AAAAAAD/////AQAAAAAAAAAAA2oBAAAAAAAKDwECAwQFBgcICQ8BAgMEBQYHCAkKCwwNDg8KDwECAwQFBgcIEA8BAgMEBQYHCAkKCwwNDg8ACg8BAgMEBQYHCAkPAQIDBAUGBwgJCgsMDQ4PCg8BAgMEBQYHCBAPAQIDBAUGBwgJCgsMDQ4PAAoPAQIDBAUGBwgJDwECAwQFBgcICQoLDA0ODwoPAQIDBAUGBwgQDwECAwQFBgcICQoLDA0ODwA="
         }
     ],
     "finalizer" : [
diff --git a/test/functional/rpc_psbt.py b/test/functional/rpc_psbt.py
index 6b1bc414a9f..e85a3372187 100755
--- a/test/functional/rpc_psbt.py
+++ b/test/functional/rpc_psbt.py
@@ -76,6 +76,26 @@ class PSBTTest(BitcoinTestFramework):
     def skip_test_if_missing_module(self):
         self.skip_if_no_wallet()
 
+    @staticmethod
+    def create_psbt(inputs=None, outputs=None):
+        if inputs is None:
+            inputs = {}
+        if outputs is None:
+            outputs = {}
+        tx = CTransaction()
+        tx.vin = [CTxIn(outpoint=COutPoint(hash=0, n=0))]
+        tx.vout = [CTxOut(nValue=1, scriptPubKey=CScript([OP_TRUE]))]
+
+        # https://github.com/bitcoin/bips/blob/master/bip-0174.mediawiki#specification
+        psbt = PSBT()
+        # global map
+        psbt.g = PSBTMap({PSBT_GLOBAL_UNSIGNED_TX: tx.serialize()})
+        # input map
+        psbt.i = [PSBTMap(inputs)]
+        # output map
+        psbt.o = [PSBTMap(outputs)]
+        return psbt
+
     def test_psbt_incomplete_after_invalid_modification(self):
         self.log.info("Check that PSBT is correctly marked as incomplete after invalid modification")
         node = self.nodes[2]
@@ -791,13 +811,24 @@ class PSBTTest(BitcoinTestFramework):
         assert_raises_rpc_error(-4, "Insufficient funds", wunsafe.walletcreatefundedpsbt, [], [{self.nodes[0].getnewaddress(): 1}])
         wunsafe.walletcreatefundedpsbt([], [{self.nodes[0].getnewaddress(): 1}], 0, {"include_unsafe": True})
 
-        # BIP 174 Test Vectors
+        self.log.info("Test that unknown values are just passed through")
+        unknown_type = b'\xf0'
+        unknown_key = unknown_type + bytes(range(1, 10))
+        unknown_value = bytes(range(1, 16))
 
-        # Check that unknown values are just passed through
-        unknown_psbt = "cHNidP8BAD8CAAAAAf//////////////////////////////////////////AAAAAAD/////AQAAAAAAAAAAA2oBAAAAAAAACg8BAgMEBQYHCAkPAQIDBAUGBwgJCgsMDQ4PAAA="
+        unknown_psbt = self.create_psbt(inputs={unknown_key: unknown_value}).to_base64()
         unknown_out = self.nodes[0].walletprocesspsbt(unknown_psbt)['psbt']
         assert_equal(unknown_psbt, unknown_out)
 
+        unknown_key2 = unknown_type + bytes(range(1, 9)) + bytes(11)
+        unknown_psbt2 = self.create_psbt(inputs={unknown_key2: unknown_value}).to_base64()
+        merged_unknown = self.nodes[0].combinepsbt([unknown_psbt, unknown_psbt2])
+        merged_unknown_psbt = PSBT.from_base64(merged_unknown)
+        assert_equal(merged_unknown_psbt.i[0].map[unknown_key], unknown_value)
+        assert_equal(merged_unknown_psbt.i[0].map[unknown_key2], unknown_value)
+
+        # BIP 174 Test Vectors
+
         # Open the data file
         with open(os.path.join(os.path.dirname(os.path.realpath(__file__)), 'data/rpc_psbt.json')) as f:
             d = json.load(f)