diff --git a/sway-lib-std/src/token.sw b/sway-lib-std/src/token.sw
index be1b90c0c7e..3298860cff0 100644
--- a/sway-lib-std/src/token.sw
+++ b/sway-lib-std/src/token.sw
@@ -87,8 +87,6 @@ pub fn force_transfer_to_contract(amount: u64, asset_id: ContractId, to: Contrac
 /// Transfer `amount` coins of type `asset_id` and send them to
 /// the address `to`.
 pub fn transfer_to_output(amount: u64, asset_id: ContractId, to: Address) {
-    const OUTPUT_VARIABLE_TYPE: u8 = 4;
-
     // maintain a manual index as we only have `while` loops in sway atm:
     let mut index = 0;
     let mut output_index = 0;
@@ -99,7 +97,7 @@ pub fn transfer_to_output(amount: u64, asset_id: ContractId, to: Address) {
     // variable output with a value of zero is by definition unused.
     let outputs_count = tx_outputs_count();
     while index < outputs_count {
-        if tx_output_type(index) == OUTPUT_VARIABLE_TYPE && tx_output_amount(index) == 0 {
+        if tx_output_type(index) == OUTPUT_VARIABLE && tx_output_amount(index) == 0 {
             output_index = index;
             output_found = true;
             break; // break early and use the output we found
diff --git a/sway-lib-std/src/tx.sw b/sway-lib-std/src/tx.sw
index ba2b6e64f4d..de696db9148 100644
--- a/sway-lib-std/src/tx.sw
+++ b/sway-lib-std/src/tx.sw
@@ -44,6 +44,19 @@ const TX_WITNESSES_COUNT_OFFSET = 10312;
 const TX_RECEIPTS_ROOT_OFFSET = 10320;
 const TX_SCRIPT_START_OFFSET = 10352;
 
+// Input types
+const INPUT_COIN = 0u8;
+const INPUT_CONTRACT = 1u8;
+const INPUT_MESSAGE = 2u8;
+
+// Output types
+const OUTPUT_COIN = 0u8;
+const OUTPUT_CONTRACT = 1u8;
+const OUTPUT_MESSAGE = 2u8;
+const OUTPUT_CHANGE = 3u8;
+const OUTPUT_VARIABLE = 4u8;
+const OUTPUT_CONTRACT_CREATED = 5u8;
+
 /// Get the transaction type.
 pub fn tx_type() -> u8 {
     asm(r1, r2: TX_TYPE_OFFSET) {