diff --git a/l1-contracts/test/fee_portal/depositToAztecPublic.t.sol b/l1-contracts/test/fee_portal/depositToAztecPublic.t.sol
index db038cfe772a..fc68df1a4441 100644
--- a/l1-contracts/test/fee_portal/depositToAztecPublic.t.sol
+++ b/l1-contracts/test/fee_portal/depositToAztecPublic.t.sol
@@ -81,6 +81,8 @@ contract DepositToAztecPublic is Test {
     uint256 amount = 100 ether;
     uint256 expectedIndex = 2 ** Constants.L1_TO_L2_MSG_SUBTREE_HEIGHT;
 
+    // The purpose of including the function selector is to make the message unique to that specific call. Note that
+    // it has nothing to do with calling the function.
     DataStructures.L1ToL2Msg memory message = DataStructures.L1ToL2Msg({
       sender: DataStructures.L1Actor(address(feeJuicePortal), block.chainid),
       recipient: DataStructures.L2Actor(feeJuicePortal.L2_TOKEN_ADDRESS(), 1 + numberOfRollups),
diff --git a/l1-contracts/test/portals/TokenPortal.sol b/l1-contracts/test/portals/TokenPortal.sol
index a2f67e047486..115132e52346 100644
--- a/l1-contracts/test/portals/TokenPortal.sol
+++ b/l1-contracts/test/portals/TokenPortal.sol
@@ -53,6 +53,8 @@ contract TokenPortal {
     DataStructures.L2Actor memory actor = DataStructures.L2Actor(l2Bridge, 1);
 
     // Hash the message content to be reconstructed in the receiving contract
+    // The purpose of including the function selector is to make the message unique to that specific call. Note that
+    // it has nothing to do with calling the function.
     bytes32 contentHash =
       Hash.sha256ToField(abi.encodeWithSignature("mint_to_public(bytes32,uint256)", _to, _amount));
 
@@ -123,6 +125,8 @@ contract TokenPortal {
     uint256 _leafIndex,
     bytes32[] calldata _path
   ) external {
+    // The purpose of including the function selector is to make the message unique to that specific call. Note that
+    // it has nothing to do with calling the function.
     DataStructures.L2ToL1Msg memory message = DataStructures.L2ToL1Msg({
       sender: DataStructures.L2Actor(l2Bridge, 1),
       recipient: DataStructures.L1Actor(address(this), block.chainid),
diff --git a/l1-contracts/test/portals/TokenPortal.t.sol b/l1-contracts/test/portals/TokenPortal.t.sol
index 31e8a85045d8..da7af0eb534b 100644
--- a/l1-contracts/test/portals/TokenPortal.t.sol
+++ b/l1-contracts/test/portals/TokenPortal.t.sol
@@ -88,6 +88,8 @@ contract TokenPortalTest is Test {
     view
     returns (DataStructures.L1ToL2Msg memory)
   {
+    // The purpose of including the function selector is to make the message unique to that specific call. Note that
+    // it has nothing to do with calling the function.
     return DataStructures.L1ToL2Msg({
       sender: DataStructures.L1Actor(address(tokenPortal), block.chainid),
       recipient: DataStructures.L2Actor(l2TokenAddress, 1),
@@ -102,6 +104,8 @@ contract TokenPortalTest is Test {
     view
     returns (DataStructures.L1ToL2Msg memory)
   {
+    // The purpose of including the function selector is to make the message unique to that specific call. Note that
+    // it has nothing to do with calling the function.
     return DataStructures.L1ToL2Msg({
       sender: DataStructures.L1Actor(address(tokenPortal), block.chainid),
       recipient: DataStructures.L2Actor(l2TokenAddress, 1),
@@ -171,6 +175,8 @@ contract TokenPortalTest is Test {
     internal
     returns (bytes32, bytes32)
   {
+    // The purpose of including the function selector is to make the message unique to that specific call. Note that
+    // it has nothing to do with calling the function.
     bytes32 l2ToL1Message = Hash.sha256ToField(
       DataStructures.L2ToL1Msg({
         sender: DataStructures.L2Actor({actor: l2TokenAddress, version: 1}),
diff --git a/l1-contracts/test/portals/UniswapPortal.sol b/l1-contracts/test/portals/UniswapPortal.sol
index a4eb66d8b806..37e02ee69bb6 100644
--- a/l1-contracts/test/portals/UniswapPortal.sol
+++ b/l1-contracts/test/portals/UniswapPortal.sol
@@ -87,6 +87,8 @@ contract UniswapPortal {
 
     {
       // prevent stack too deep errors
+      // The purpose of including the function selector is to make the message unique to that specific call. Note that
+      // it has nothing to do with calling the function.
       vars.contentHash = Hash.sha256ToField(
         abi.encodeWithSignature(
           "swap_public(address,uint256,uint24,address,uint256,bytes32,bytes32,address)",
@@ -191,6 +193,8 @@ contract UniswapPortal {
 
     {
       // prevent stack too deep errors
+      // The purpose of including the function selector is to make the message unique to that specific call. Note that
+      // it has nothing to do with calling the function.
       vars.contentHash = Hash.sha256ToField(
         abi.encodeWithSignature(
           "swap_private(address,uint256,uint24,address,uint256,bytes32,address)",
diff --git a/l1-contracts/test/portals/UniswapPortal.t.sol b/l1-contracts/test/portals/UniswapPortal.t.sol
index bf37ae19e64f..ac646e17bac7 100644
--- a/l1-contracts/test/portals/UniswapPortal.t.sol
+++ b/l1-contracts/test/portals/UniswapPortal.t.sol
@@ -94,6 +94,8 @@ contract UniswapPortalTest is Test {
     view
     returns (bytes32 l2ToL1MessageHash)
   {
+    // The purpose of including the function selector is to make the message unique to that specific call. Note that
+    // it has nothing to do with calling the function.
     DataStructures.L2ToL1Msg memory message = DataStructures.L2ToL1Msg({
       sender: DataStructures.L2Actor(l2TokenAddress, 1),
       recipient: DataStructures.L1Actor(address(daiTokenPortal), block.chainid),
@@ -116,6 +118,8 @@ contract UniswapPortalTest is Test {
     view
     returns (bytes32 l2ToL1MessageHash)
   {
+    // The purpose of including the function selector is to make the message unique to that specific call. Note that
+    // it has nothing to do with calling the function.
     DataStructures.L2ToL1Msg memory message = DataStructures.L2ToL1Msg({
       sender: DataStructures.L2Actor(l2UniswapAddress, 1),
       recipient: DataStructures.L1Actor(address(uniswapPortal), block.chainid),
@@ -143,6 +147,8 @@ contract UniswapPortalTest is Test {
    * Set to address(0) if anyone can call.
    */
   function _createUniswapSwapMessagePrivate(address _caller) internal view returns (bytes32) {
+    // The purpose of including the function selector is to make the message unique to that specific call. Note that
+    // it has nothing to do with calling the function.
     DataStructures.L2ToL1Msg memory message = DataStructures.L2ToL1Msg({
       sender: DataStructures.L2Actor(l2UniswapAddress, 1),
       recipient: DataStructures.L1Actor(address(uniswapPortal), block.chainid),
diff --git a/noir-projects/noir-contracts/contracts/fee_juice_contract/src/lib.nr b/noir-projects/noir-contracts/contracts/fee_juice_contract/src/lib.nr
index 6f77d74b16e9..98167e293a8d 100644
--- a/noir-projects/noir-contracts/contracts/fee_juice_contract/src/lib.nr
+++ b/noir-projects/noir-contracts/contracts/fee_juice_contract/src/lib.nr
@@ -16,11 +16,14 @@ pub fn get_bridge_gas_msg_hash(owner: AztecAddress, amount: Field) -> Field {
         hash_bytes[i + 36] = amount_bytes[i];
     }
 
-    // Function selector: 0x63f44968 keccak256('claim(bytes32,uint256)')
-    hash_bytes[0] = 0x63;
-    hash_bytes[1] = 0xf4;
-    hash_bytes[2] = 0x49;
-    hash_bytes[3] = 0x68;
+    // The purpose of including the following selector is to make the message unique to that specific call. Note that
+    // it has nothing to do with calling the function.
+    let selector = comptime { std::hash::keccak256("claim(bytes32,uint256)".as_bytes(), 22) };
+
+    hash_bytes[0] = selector[0];
+    hash_bytes[1] = selector[1];
+    hash_bytes[2] = selector[2];
+    hash_bytes[3] = selector[3];
 
     let content_hash = sha256_to_field(hash_bytes);
     content_hash
diff --git a/noir-projects/noir-contracts/contracts/token_portal_content_hash_lib/src/lib.nr b/noir-projects/noir-contracts/contracts/token_portal_content_hash_lib/src/lib.nr
index a25b24cd650a..022c4876ad25 100644
--- a/noir-projects/noir-contracts/contracts/token_portal_content_hash_lib/src/lib.nr
+++ b/noir-projects/noir-contracts/contracts/token_portal_content_hash_lib/src/lib.nr
@@ -14,7 +14,9 @@ pub fn get_mint_to_public_content_hash(owner: AztecAddress, amount: Field) -> Fi
         hash_bytes[i + 36] = amount_bytes[i];
     }
 
-    let selector = comptime { std::hash::keccak256("mint_to_public(bytes32,uint256)".as_bytes(), 24) };
+    // The purpose of including the following selector is to make the message unique to that specific call. Note that
+    // it has nothing to do with calling the function.
+    let selector = comptime { std::hash::keccak256("mint_to_public(bytes32,uint256)".as_bytes(), 31) };
 
     hash_bytes[0] = selector[0];
     hash_bytes[1] = selector[1];
@@ -39,6 +41,8 @@ pub fn get_mint_to_private_content_hash(
         hash_bytes[i + 4] = amount_bytes[i];
     }
 
+    // The purpose of including the following selector is to make the message unique to that specific call. Note that
+    // it has nothing to do with calling the function.
     let selector = comptime { std::hash::keccak256("mint_to_private(uint256)".as_bytes(), 24) };
 
     hash_bytes[0] = selector[0];
@@ -63,7 +67,9 @@ pub fn get_withdraw_content_hash(recipient: EthAddress, amount: Field, caller_on
     let amount_bytes: [u8; 32] = amount.to_be_bytes();
     let caller_on_l1_bytes: [u8; 32] = caller_on_l1.to_field().to_be_bytes();
 
-    let selector = comptime { std::hash::keccak256("withdraw(address,uint256,address)".as_bytes(), 24) };
+    // The purpose of including the following selector is to make the message unique to that specific call. Note that
+    // it has nothing to do with calling the function.
+    let selector = comptime { std::hash::keccak256("withdraw(address,uint256,address)".as_bytes(), 33) };
 
     hash_bytes[0] = selector[0];
     hash_bytes[1] = selector[1];
diff --git a/noir-projects/noir-contracts/contracts/uniswap_contract/src/util.nr b/noir-projects/noir-contracts/contracts/uniswap_contract/src/util.nr
index a0e2ca12774b..dc5605d7fd09 100644
--- a/noir-projects/noir-contracts/contracts/uniswap_contract/src/util.nr
+++ b/noir-projects/noir-contracts/contracts/uniswap_contract/src/util.nr
@@ -27,11 +27,19 @@ pub fn compute_swap_public_content_hash(
         secret_hash_for_L1_to_l2_message.to_be_bytes();
     let caller_on_L1_bytes: [u8; 32] = caller_on_L1.to_field().to_be_bytes();
 
-    // function selector: 0xf18186d8 keccak256("swap_public(address,uint256,uint24,address,uint256,bytes32,bytes32,address)")
-    hash_bytes[0] = 0xf1;
-    hash_bytes[1] = 0x81;
-    hash_bytes[2] = 0x86;
-    hash_bytes[3] = 0xd8;
+    // The purpose of including the following selector is to make the message unique to that specific call. Note that
+    // it has nothing to do with calling the function.
+    let selector = comptime {
+        std::hash::keccak256(
+            "swap_public(address,uint256,uint24,address,uint256,bytes32,bytes32,address)".as_bytes(),
+            75,
+        )
+    };
+
+    hash_bytes[0] = selector[0];
+    hash_bytes[1] = selector[1];
+    hash_bytes[2] = selector[2];
+    hash_bytes[3] = selector[3];
 
     for i in 0..32 {
         hash_bytes[i + 4] = input_token_portal_bytes[i];
@@ -73,11 +81,19 @@ pub fn compute_swap_private_content_hash(
         secret_hash_for_L1_to_l2_message.to_be_bytes();
     let caller_on_L1_bytes: [u8; 32] = caller_on_L1.to_field().to_be_bytes();
 
-    // function selector: 0x84e55078 keccak256("swap_private(address,uint256,uint24,address,uint256,bytes32,address)")
-    hash_bytes[0] = 0x84;
-    hash_bytes[1] = 0xe5;
-    hash_bytes[2] = 0x50;
-    hash_bytes[3] = 0x78;
+    // The purpose of including the following selector is to make the message unique to that specific call. Note that
+    // it has nothing to do with calling the function.
+    let selector = comptime {
+        std::hash::keccak256(
+            "swap_private(address,uint256,uint24,address,uint256,bytes32,address)".as_bytes(),
+            68,
+        )
+    };
+
+    hash_bytes[0] = selector[0];
+    hash_bytes[1] = selector[1];
+    hash_bytes[2] = selector[2];
+    hash_bytes[3] = selector[3];
 
     for i in 0..32 {
         hash_bytes[i + 4] = input_token_portal_bytes[i];