diff --git a/.gitmodules b/.gitmodules
index d4abc92..59dbe0d 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -1,15 +1,9 @@
-[submodule "lib/bitcoin-spv"]
-	path = lib/bitcoin-spv
-	url = https://github.com/summa-tx/bitcoin-spv
 [submodule "lib/forge-std"]
 	path = lib/forge-std
 	url = https://github.com/foundry-rs/forge-std
 [submodule "lib/foundry-devops"]
 	path = lib/foundry-devops
 	url = https://github.com/Cyfrin/foundry-devops
-[submodule "lib/solmate"]
-	path = lib/solmate
-	url = https://github.com/transmissions11/solmate
 [submodule "lib/elliptic-curve-solidity"]
 	path = lib/elliptic-curve-solidity
 	url = https://github.com/witnet/elliptic-curve-solidity
diff --git a/lib/bitcoin-spv b/lib/bitcoin-spv
deleted file mode 160000
index 362cfd9..0000000
--- a/lib/bitcoin-spv
+++ /dev/null
@@ -1 +0,0 @@
-Subproject commit 362cfd9ac6ad1ea15d14920bbe97b2c0c017016a
diff --git a/lib/solmate b/lib/solmate
deleted file mode 160000
index c892309..0000000
--- a/lib/solmate
+++ /dev/null
@@ -1 +0,0 @@
-Subproject commit c892309933b25c03d32b1b0d674df7ae292ba925
diff --git a/src/BTCDepositAddressDeriver.sol b/src/BTCDepositAddressDeriver.sol
index 4bf6456..75d6fac 100644
--- a/src/BTCDepositAddressDeriver.sol
+++ b/src/BTCDepositAddressDeriver.sol
@@ -1,6 +1,6 @@
 // SPDX-License-Identifier: MIT
 
-pragma solidity ^0.8.13;
+pragma solidity ^0.8.18;
 
 import {Deriver} from "./Deriver.sol";
 import {Bech32m} from "./Bech32m.sol";
@@ -54,9 +54,9 @@ contract BTCDepositAddressDeriver {
     }
 
     function setSeed(
-        string memory _btcAddr1,
-        string memory _btcAddr2,
-        string memory _hrp
+        string calldata _btcAddr1,
+        string calldata _btcAddr2,
+        string calldata _hrp
     ) public virtual {
         networkHrp = _hrp;
         (p1x, p1y) = parseBTCTaprootAddress(_hrp, _btcAddr1);
diff --git a/src/Bech32m.sol b/src/Bech32m.sol
index 0574833..c8ddaa3 100644
--- a/src/Bech32m.sol
+++ b/src/Bech32m.sol
@@ -2,7 +2,7 @@
 // TODO(mkl): what License?
 // based on https://github.com/bitcoin/bips/blob/master/bip-0350.mediawiki
 // https://github.com/sipa/bech32/blob/master/ref/python/segwit_addr.py
-pragma solidity ^0.8;
+pragma solidity ^0.8.18;
 
 error EncodingIsUnknown();
 
@@ -64,6 +64,9 @@ library Bech32m {
     // BECH32M_CONST = 0x2bc830a3
     uint256 public constant BECH32M_CONST = 0x2bc830a3;
 
+    // 1 byte for the separator
+    bytes1 public constant SEPARATOR = bytes1(0x31);
+
     // TODO(mkl): port implementation from C++ reference because it is more readable
     // https://github.com/sipa/bech32/blob/master/ref/c%2B%2B/bech32.cpp
     //     /** This function will compute what 6 5-bit values to XOR into the last 6 input values, in order to
@@ -267,9 +270,6 @@ library Bech32m {
 
         // <hrp> 1 <data-5bit-format> <6bytes of chk-5bit-format>
 
-        // 1 byte for the separator
-        bytes1 constant SEPARATOR = bytes1(0x31);
-
         // reuse data and chk arrays to modify data in place to save gas
 
         for (uint i = 0; i < data.length; i += 1) {
diff --git a/src/Deriver.sol b/src/Deriver.sol
index 210f761..acce20b 100644
--- a/src/Deriver.sol
+++ b/src/Deriver.sol
@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: UNLICENSED
-pragma solidity ^0.8.13;
+pragma solidity ^0.8.18;
 
 import {EllipticCurve} from "../lib/elliptic-curve-solidity/contracts/EllipticCurve.sol";