diff --git a/yarn-project/types/src/abi/contract_artifact.ts b/yarn-project/types/src/abi/contract_artifact.ts
index 2182451baf46..4c52434bf0e1 100644
--- a/yarn-project/types/src/abi/contract_artifact.ts
+++ b/yarn-project/types/src/abi/contract_artifact.ts
@@ -128,8 +128,8 @@ function generateFunctionArtifact(
   }
 
   let returnTypes: AbiType[] = [];
-  if (functionType === FunctionType.UNCONSTRAINED && fn.abi.return_type) {
-    returnTypes = [fn.abi.return_type.abi_type];
+  if (functionType === FunctionType.UNCONSTRAINED) {
+    returnTypes = fn.abi.return_type ? [fn.abi.return_type.abi_type] : returnTypes;
   } else {
     const pathToFind = `${contract.name}::${fn.name}_abi`;
     const abiStructs: AbiType[] = contract.outputs.structs['functions'];