diff --git a/test/functional/p2p-fullblocktest.py b/test/functional/p2p-fullblocktest.py
index 010dbdccad..8d85a4a934 100755
--- a/test/functional/p2p-fullblocktest.py
+++ b/test/functional/p2p-fullblocktest.py
@@ -36,12 +36,15 @@ class CBrokenBlock(CBlock):
         self.vtx = copy.deepcopy(base_block.vtx)
         self.hashMerkleRoot = self.calc_merkle_root()
 
-    def serialize(self):
+    def serialize(self, with_witness=False):
         r = b""
         r += super(CBlock, self).serialize()
         r += struct.pack("<BQ", 255, len(self.vtx))
         for tx in self.vtx:
-            r += tx.serialize()
+            if with_witness:
+                r += tx.serialize_with_witness()
+            else:
+                r += tx.serialize_without_witness()
         return r
 
     def normal_serialize(self):
diff --git a/test/functional/p2p-segwit.py b/test/functional/p2p-segwit.py
index a06601c38e..26de0119cd 100755
--- a/test/functional/p2p-segwit.py
+++ b/test/functional/p2p-segwit.py
@@ -25,7 +25,7 @@ MAX_SIGOP_COST = 80000
 # Calculate the virtual size of a witness block:
 # (base + witness/4)
 def get_virtual_size(witness_block):
-    base_size = len(witness_block.serialize())
+    base_size = len(witness_block.serialize(with_witness=False))
     total_size = len(witness_block.serialize(with_witness=True))
     # the "+3" is so we round up
     vsize = int((3*base_size + total_size + 3)/4)
diff --git a/test/functional/test_framework/messages.py b/test/functional/test_framework/messages.py
index 2ab1bdac0f..c5c640f8f9 100644
--- a/test/functional/test_framework/messages.py
+++ b/test/functional/test_framework/messages.py
@@ -452,10 +452,10 @@ class CTransaction():
         r += struct.pack("<I", self.nLockTime)
         return r
 
-    # Regular serialization is without witness -- must explicitly
-    # call serialize_with_witness to include witness data.
+    # Regular serialization is with witness -- must explicitly
+    # call serialize_without_witness to exclude witness data.
     def serialize(self):
-        return self.serialize_without_witness()
+        return self.serialize_with_witness()
 
     # Recalculate the txid (transaction hash without witness)
     def rehash(self):
@@ -471,7 +471,7 @@ class CTransaction():
 
         if self.sha256 is None:
             self.sha256 = uint256_from_str(hash256(self.serialize_without_witness()))
-        self.hash = encode(hash256(self.serialize())[::-1], 'hex_codec').decode('ascii')
+        self.hash = encode(hash256(self.serialize_without_witness())[::-1], 'hex_codec').decode('ascii')
 
     def is_valid(self):
         self.calc_sha256()
@@ -568,7 +568,7 @@ class CBlock(CBlockHeader):
         if with_witness:
             r += ser_vector(self.vtx, "serialize_with_witness")
         else:
-            r += ser_vector(self.vtx)
+            r += ser_vector(self.vtx, "serialize_without_witness")
         return r
 
     # Calculate the merkle root given a vector of transaction hashes
@@ -635,7 +635,7 @@ class PrefilledTransaction():
         self.tx = CTransaction()
         self.tx.deserialize(f)
 
-    def serialize(self, with_witness=False):
+    def serialize(self, with_witness=True):
         r = b""
         r += ser_compact_size(self.index)
         if with_witness:
@@ -644,6 +644,9 @@ class PrefilledTransaction():
             r += self.tx.serialize_without_witness()
         return r
 
+    def serialize_without_witness(self):
+        return self.serialize(with_witness=False)
+
     def serialize_with_witness(self):
         return self.serialize(with_witness=True)
 
@@ -683,7 +686,7 @@ class P2PHeaderAndShortIDs():
         if with_witness:
             r += ser_vector(self.prefilled_txn, "serialize_with_witness")
         else:
-            r += ser_vector(self.prefilled_txn)
+            r += ser_vector(self.prefilled_txn, "serialize_without_witness")
         return r
 
     def __repr__(self):
@@ -814,13 +817,13 @@ class BlockTransactions():
         self.blockhash = deser_uint256(f)
         self.transactions = deser_vector(f, CTransaction)
 
-    def serialize(self, with_witness=False):
+    def serialize(self, with_witness=True):
         r = b""
         r += ser_uint256(self.blockhash)
         if with_witness:
             r += ser_vector(self.transactions, "serialize_with_witness")
         else:
-            r += ser_vector(self.transactions)
+            r += ser_vector(self.transactions, "serialize_without_witness")
         return r
 
     def __repr__(self):
@@ -1020,7 +1023,7 @@ class msg_block():
         self.block.deserialize(f)
 
     def serialize(self):
-        return self.block.serialize()
+        return self.block.serialize(with_witness=False)
 
     def __repr__(self):
         return "msg_block(block=%s)" % (repr(self.block))
@@ -1291,7 +1294,7 @@ class msg_blocktxn():
 
     def serialize(self):
         r = b""
-        r += self.block_transactions.serialize()
+        r += self.block_transactions.serialize(with_witness=False)
         return r
 
     def __repr__(self):
diff --git a/test/functional/test_framework/script.py b/test/functional/test_framework/script.py
index a4c046bd3d..79382cc6d5 100644
--- a/test/functional/test_framework/script.py
+++ b/test/functional/test_framework/script.py
@@ -641,7 +641,7 @@ def SignatureHash(script, txTo, inIdx, hashtype):
         txtmp.vin = []
         txtmp.vin.append(tmp)
 
-    s = txtmp.serialize()
+    s = txtmp.serialize_without_witness()
     s += struct.pack(b"<I", hashtype)
 
     hash = hash256(s)