diff --git a/electrum/bitcoin.py b/electrum/bitcoin.py
index f716ac67b..35e17dc39 100644
--- a/electrum/bitcoin.py
+++ b/electrum/bitcoin.py
@@ -23,7 +23,7 @@
 # CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 # SOFTWARE.
 
-from typing import Tuple, TYPE_CHECKING, Optional, Union, Sequence
+from typing import Tuple, TYPE_CHECKING, Optional, Union, Sequence, Mapping, Any
 import enum
 from enum import IntEnum, Enum
 
@@ -37,6 +37,7 @@ from .crypto import sha256d, sha256, hash_160
 
 if TYPE_CHECKING:
     from .network import Network
+    from .transaction import OPPushDataGeneric
 
 
 ################################## transactions
@@ -295,12 +296,18 @@ def construct_witness(items: Sequence[Union[str, int, bytes]]) -> bytes:
     return bytes(witness)
 
 
-def construct_script(items: Sequence[Union[str, int, bytes, opcodes]], values=None) -> bytes:
+def construct_script(
+    items: Sequence[Union[str, int, bytes, opcodes, 'OPPushDataGeneric']],
+    *,
+    values: Optional[Mapping[int, Any]] = None,  # can be used to substitute into OPPushDataGeneric
+) -> bytes:
     """Constructs bitcoin script from given items."""
+    from .transaction import OPPushDataGeneric
     script = bytearray()
     values = values or {}
     for i, item in enumerate(items):
         if i in values:
+            assert OPPushDataGeneric.is_instance(item), f"tried to substitute into {item=!r}"
             item = values[i]
         if isinstance(item, opcodes):
             script += bytes([item])
@@ -312,7 +319,7 @@ def construct_script(items: Sequence[Union[str, int, bytes, opcodes]], values=No
             assert is_hex_str(item)
             script += push_script(bfh(item))
         else:
-            raise Exception(f'unexpected item for script: {item!r}')
+            raise Exception(f'unexpected item for script: {item!r} at idx={i}')
     return bytes(script)
 
 
diff --git a/electrum/lnutil.py b/electrum/lnutil.py
index 083a620d6..2a760b278 100644
--- a/electrum/lnutil.py
+++ b/electrum/lnutil.py
@@ -774,37 +774,17 @@ def make_offered_htlc(
     assert type(remote_htlcpubkey) is bytes
     assert type(local_htlcpubkey) is bytes
     assert type(payment_hash) is bytes
-    script_opcodes = [
-        opcodes.OP_DUP,
-        opcodes.OP_HASH160,
-        bitcoin.hash_160(revocation_pubkey),
-        opcodes.OP_EQUAL,
-        opcodes.OP_IF,
-        opcodes.OP_CHECKSIG,
-        opcodes.OP_ELSE,
-        remote_htlcpubkey,
-        opcodes.OP_SWAP,
-        opcodes.OP_SIZE,
-        32,
-        opcodes.OP_EQUAL,
-        opcodes.OP_NOTIF,
-        opcodes.OP_DROP,
-        2,
-        opcodes.OP_SWAP,
-        local_htlcpubkey,
-        2,
-        opcodes.OP_CHECKMULTISIG,
-        opcodes.OP_ELSE,
-        opcodes.OP_HASH160,
-        crypto.ripemd(payment_hash),
-        opcodes.OP_EQUALVERIFY,
-        opcodes.OP_CHECKSIG,
-        opcodes.OP_ENDIF,
-    ]
-    if has_anchors:
-        script_opcodes.extend([1, opcodes.OP_CHECKSEQUENCEVERIFY, opcodes.OP_DROP])
-    script_opcodes.append(opcodes.OP_ENDIF)
-    script = construct_script(script_opcodes)
+    script_template = witness_template_offered_htlc(anchors=has_anchors)
+    script = construct_script(
+        script_template,
+        values={
+            2: bitcoin.hash_160(revocation_pubkey),
+            7: remote_htlcpubkey,
+            10: 32,
+            16: local_htlcpubkey,
+            21: crypto.ripemd(payment_hash),
+        },
+    )
     return script
 
 
@@ -820,105 +800,104 @@ def make_received_htlc(
     for i in [revocation_pubkey, remote_htlcpubkey, local_htlcpubkey, payment_hash]:
         assert type(i) is bytes
     assert type(cltv_abs) is int
+    script_template = witness_template_received_htlc(anchors=has_anchors)
+    script = construct_script(
+        script_template,
+        values={
+            2: bitcoin.hash_160(revocation_pubkey),
+            7: remote_htlcpubkey,
+            10: 32,
+            14: crypto.ripemd(payment_hash),
+            18: local_htlcpubkey,
+            23: cltv_abs,
+        },
+    )
+    return script
 
-    script_opcodes = [
+
+def witness_template_offered_htlc(anchors: bool):
+    return [
         opcodes.OP_DUP,
         opcodes.OP_HASH160,
-        bitcoin.hash_160(revocation_pubkey),
+        OPPushDataGeneric(None),
         opcodes.OP_EQUAL,
         opcodes.OP_IF,
         opcodes.OP_CHECKSIG,
         opcodes.OP_ELSE,
-        remote_htlcpubkey,
+        OPPushDataGeneric(None),
         opcodes.OP_SWAP,
         opcodes.OP_SIZE,
-        32,
+        OPPushDataGeneric(lambda x: x==1),
+        opcodes.OP_EQUAL,
+        opcodes.OP_NOTIF,
+        opcodes.OP_DROP,
+        opcodes.OP_2,
+        opcodes.OP_SWAP,
+        OPPushDataGeneric(None),
+        opcodes.OP_2,
+        opcodes.OP_CHECKMULTISIG,
+        opcodes.OP_ELSE,
+        opcodes.OP_HASH160,
+        OPPushDataGeneric(None),
+        opcodes.OP_EQUALVERIFY,
+        opcodes.OP_CHECKSIG,
+        opcodes.OP_ENDIF,
+    ] + ([
+        opcodes.OP_1,
+        opcodes.OP_CHECKSEQUENCEVERIFY,
+        opcodes.OP_DROP,
+    ] if anchors else [
+    ]) + [
+        opcodes.OP_ENDIF,
+    ]
+
+
+WITNESS_TEMPLATE_OFFERED_HTLC = witness_template_offered_htlc(anchors=False)
+WITNESS_TEMPLATE_OFFERED_HTLC_ANCHORS = witness_template_offered_htlc(anchors=True)
+
+
+def witness_template_received_htlc(anchors: bool):
+    return [
+        opcodes.OP_DUP,
+        opcodes.OP_HASH160,
+        OPPushDataGeneric(None),
+        opcodes.OP_EQUAL,
+        opcodes.OP_IF,
+        opcodes.OP_CHECKSIG,
+        opcodes.OP_ELSE,
+        OPPushDataGeneric(None),
+        opcodes.OP_SWAP,
+        opcodes.OP_SIZE,
+        OPPushDataGeneric(lambda x: x==1),
         opcodes.OP_EQUAL,
         opcodes.OP_IF,
         opcodes.OP_HASH160,
-        crypto.ripemd(payment_hash),
+        OPPushDataGeneric(None),
         opcodes.OP_EQUALVERIFY,
-        2,
+        opcodes.OP_2,
         opcodes.OP_SWAP,
-        local_htlcpubkey,
-        2,
+        OPPushDataGeneric(None),
+        opcodes.OP_2,
         opcodes.OP_CHECKMULTISIG,
         opcodes.OP_ELSE,
         opcodes.OP_DROP,
-        cltv_abs,
+        OPPushDataGeneric(None),
         opcodes.OP_CHECKLOCKTIMEVERIFY,
         opcodes.OP_DROP,
         opcodes.OP_CHECKSIG,
         opcodes.OP_ENDIF,
+    ] + ([
+        opcodes.OP_1,
+        opcodes.OP_CHECKSEQUENCEVERIFY,
+        opcodes.OP_DROP,
+    ] if anchors else [
+    ]) + [
+        opcodes.OP_ENDIF,
     ]
-    if has_anchors:
-        script_opcodes.extend([1, opcodes.OP_CHECKSEQUENCEVERIFY, opcodes.OP_DROP])
-    script_opcodes.append(opcodes.OP_ENDIF)
-    script = construct_script(script_opcodes)
-    return script
 
 
-WITNESS_TEMPLATE_OFFERED_HTLC = [
-    opcodes.OP_DUP,
-    opcodes.OP_HASH160,
-    OPPushDataGeneric(None),
-    opcodes.OP_EQUAL,
-    opcodes.OP_IF,
-    opcodes.OP_CHECKSIG,
-    opcodes.OP_ELSE,
-    OPPushDataGeneric(None),
-    opcodes.OP_SWAP,
-    opcodes.OP_SIZE,
-    OPPushDataGeneric(lambda x: x==1),
-    opcodes.OP_EQUAL,
-    opcodes.OP_NOTIF,
-    opcodes.OP_DROP,
-    opcodes.OP_2,
-    opcodes.OP_SWAP,
-    OPPushDataGeneric(None),
-    opcodes.OP_2,
-    opcodes.OP_CHECKMULTISIG,
-    opcodes.OP_ELSE,
-    opcodes.OP_HASH160,
-    OPPushDataGeneric(None),
-    opcodes.OP_EQUALVERIFY,
-    opcodes.OP_CHECKSIG,
-    opcodes.OP_ENDIF,
-    opcodes.OP_ENDIF,
-]
-
-
-WITNESS_TEMPLATE_RECEIVED_HTLC = [
-    opcodes.OP_DUP,
-    opcodes.OP_HASH160,
-    OPPushDataGeneric(None),
-    opcodes.OP_EQUAL,
-    opcodes.OP_IF,
-    opcodes.OP_CHECKSIG,
-    opcodes.OP_ELSE,
-    OPPushDataGeneric(None),
-    opcodes.OP_SWAP,
-    opcodes.OP_SIZE,
-    OPPushDataGeneric(lambda x: x==1),
-    opcodes.OP_EQUAL,
-    opcodes.OP_IF,
-    opcodes.OP_HASH160,
-    OPPushDataGeneric(None),
-    opcodes.OP_EQUALVERIFY,
-    opcodes.OP_2,
-    opcodes.OP_SWAP,
-    OPPushDataGeneric(None),
-    opcodes.OP_2,
-    opcodes.OP_CHECKMULTISIG,
-    opcodes.OP_ELSE,
-    opcodes.OP_DROP,
-    OPPushDataGeneric(None),
-    opcodes.OP_CHECKLOCKTIMEVERIFY,
-    opcodes.OP_DROP,
-    opcodes.OP_CHECKSIG,
-    opcodes.OP_ENDIF,
-    opcodes.OP_ENDIF,
-]
+WITNESS_TEMPLATE_RECEIVED_HTLC = witness_template_received_htlc(anchors=False)
+WITNESS_TEMPLATE_RECEIVED_HTLC_ANCHORS = witness_template_received_htlc(anchors=True)
 
 
 def make_htlc_output_witness_script(
diff --git a/electrum/submarine_swaps.py b/electrum/submarine_swaps.py
index 7392103d6..fab40f8c0 100644
--- a/electrum/submarine_swaps.py
+++ b/electrum/submarine_swaps.py
@@ -516,7 +516,7 @@ class SwapManager(Logger):
         onchain_amount_sat = self._get_recv_amount(lightning_amount_sat, is_reverse=True) # what the client is going to receive
         redeem_script = construct_script(
             WITNESS_TEMPLATE_REVERSE_SWAP,
-            {1:32, 5:ripemd(payment_hash), 7:their_pubkey, 10:locktime, 13:our_pubkey}
+            values={1:32, 5:ripemd(payment_hash), 7:their_pubkey, 10:locktime, 13:our_pubkey}
         )
         swap, invoice, prepay_invoice = self.add_normal_swap(
             redeem_script=redeem_script,
@@ -611,7 +611,7 @@ class SwapManager(Logger):
         payment_hash = sha256(preimage)
         redeem_script = construct_script(
             WITNESS_TEMPLATE_REVERSE_SWAP,
-            {1:32, 5:ripemd(payment_hash), 7:our_pubkey, 10:locktime, 13:their_pubkey}
+            values={1:32, 5:ripemd(payment_hash), 7:our_pubkey, 10:locktime, 13:their_pubkey}
         )
         swap = self.add_reverse_swap(
             redeem_script=redeem_script,