diff --git a/contracts/src/main/kotlin/com/r3corda/contracts/IRS.kt b/contracts/src/main/kotlin/com/r3corda/contracts/IRS.kt
index 65b4ff6fea..773b095acd 100644
--- a/contracts/src/main/kotlin/com/r3corda/contracts/IRS.kt
+++ b/contracts/src/main/kotlin/com/r3corda/contracts/IRS.kt
@@ -461,7 +461,7 @@ class InterestRateSwap() : ClauseVerifier() {
             override val ifNotMatched = MatchBehaviour.CONTINUE
 
             // These functions may make more sense to use for basket types, but for now let's leave them here
-            fun checkLegDates(legs: Array<CommonLeg>) {
+            fun checkLegDates(legs: List<CommonLeg>) {
                 requireThat {
                     "Effective date is before termination date" by legs.all { it.effectiveDate < it.terminationDate }
                     "Effective dates are in alignment" by legs.all { it.effectiveDate == legs[0].effectiveDate }
@@ -469,7 +469,7 @@ class InterestRateSwap() : ClauseVerifier() {
                 }
             }
 
-            fun checkLegAmounts(legs: Array<CommonLeg>) {
+            fun checkLegAmounts(legs: List<CommonLeg>) {
                 requireThat {
                     "The notional is non zero" by legs.any { it.notional.quantity > (0).toLong() }
                     "The notional for all legs must be the same" by legs.all { it.notional == legs[0].notional }
@@ -485,9 +485,9 @@ class InterestRateSwap() : ClauseVerifier() {
             }
 
             // TODO: After business rules discussion, add further checks to the schedules and rates
-            fun checkSchedules(@Suppress("UNUSED_PARAMETER") legs: Array<CommonLeg>): Boolean = true
+            fun checkSchedules(@Suppress("UNUSED_PARAMETER") legs: List<CommonLeg>): Boolean = true
 
-            fun checkRates(@Suppress("UNUSED_PARAMETER") legs: Array<CommonLeg>): Boolean = true
+            fun checkRates(@Suppress("UNUSED_PARAMETER") legs: List<CommonLeg>): Boolean = true
 
             /**
              * Compares two schedules of Floating Leg Payments, returns the difference (i.e. omissions in either leg or changes to the values).
@@ -550,14 +550,14 @@ class InterestRateSwap() : ClauseVerifier() {
                     "The effective date is before the termination date for the floating leg" by (irs.floatingLeg.effectiveDate < irs.floatingLeg.terminationDate)
                     "The effective dates are aligned" by (irs.floatingLeg.effectiveDate == irs.fixedLeg.effectiveDate)
                     "The termination dates are aligned" by (irs.floatingLeg.terminationDate == irs.fixedLeg.terminationDate)
-                    "The rates are valid" by checkRates(arrayOf(irs.fixedLeg, irs.floatingLeg))
-                    "The schedules are valid" by checkSchedules(arrayOf(irs.fixedLeg, irs.floatingLeg))
+                    "The rates are valid" by checkRates(listOf(irs.fixedLeg, irs.floatingLeg))
+                    "The schedules are valid" by checkSchedules(listOf(irs.fixedLeg, irs.floatingLeg))
                     "The fixing period date offset cannot be negative" by (irs.floatingLeg.fixingPeriodOffset >= 0)
 
                     // TODO: further tests
                 }
-                checkLegAmounts(arrayOf(irs.fixedLeg, irs.floatingLeg))
-                checkLegDates(arrayOf(irs.fixedLeg, irs.floatingLeg))
+                checkLegAmounts(listOf(irs.fixedLeg, irs.floatingLeg))
+                checkLegDates(listOf(irs.fixedLeg, irs.floatingLeg))
 
                 return setOf(command.value)
             }
@@ -672,8 +672,8 @@ class InterestRateSwap() : ClauseVerifier() {
             return (fixedLeg.fixedRatePayer.owningKey in ourKeys) || (floatingLeg.floatingRatePayer.owningKey in ourKeys)
         }
 
-        override val parties: Array<Party>
-            get() = arrayOf(fixedLeg.fixedRatePayer, floatingLeg.floatingRatePayer)
+        override val parties: List<Party>
+            get() = listOf(fixedLeg.fixedRatePayer, floatingLeg.floatingRatePayer)
 
         override fun nextScheduledActivity(thisStateRef: StateRef, protocolLogicRefFactory: ProtocolLogicRefFactory): ScheduledActivity? {
             val nextFixingOf = nextFixingOf() ?: return null
diff --git a/core/src/main/kotlin/com/r3corda/core/contracts/Structures.kt b/core/src/main/kotlin/com/r3corda/core/contracts/Structures.kt
index bfa70fdaa0..9815225118 100644
--- a/core/src/main/kotlin/com/r3corda/core/contracts/Structures.kt
+++ b/core/src/main/kotlin/com/r3corda/core/contracts/Structures.kt
@@ -230,7 +230,7 @@ interface DealState : LinearState {
     val ref: String
 
     /** Exposes the Parties involved in a generic way */
-    val parties: Array<Party>
+    val parties: List<Party>
 
     // TODO: This works by editing the keys used by a Party which is invalid.
     fun withPublicKey(before: Party, after: PublicKey): DealState
diff --git a/src/main/kotlin/com/r3corda/demos/protocols/AutoOfferProtocol.kt b/src/main/kotlin/com/r3corda/demos/protocols/AutoOfferProtocol.kt
index 047e9a10da..11ff47d0ea 100644
--- a/src/main/kotlin/com/r3corda/demos/protocols/AutoOfferProtocol.kt
+++ b/src/main/kotlin/com/r3corda/demos/protocols/AutoOfferProtocol.kt
@@ -102,7 +102,7 @@ object AutoOfferProtocol {
 
             val notary = serviceHub.networkMapCache.notaryNodes.first().identity
             // need to pick which ever party is not us
-            val otherParty = notUs(*dealToBeOffered.parties).single()
+            val otherParty = notUs(dealToBeOffered.parties).single()
             progressTracker.currentStep = ANNOUNCING
             send(otherParty, 0, AutoOfferMessage(serviceHub.storageService.myLegalIdentity, notary, ourSessionID, dealToBeOffered))
             progressTracker.currentStep = DEALING
@@ -110,7 +110,7 @@ object AutoOfferProtocol {
             return stx
         }
 
-        private fun notUs(vararg parties: Party): List<Party> {
+        private fun notUs(parties: List<Party>): List<Party> {
             val notUsParties: MutableList<Party> = arrayListOf()
             for (party in parties) {
                 if (serviceHub.storageService.myLegalIdentity != party) {