diff --git a/node/src/main/kotlin/com/r3corda/node/internal/AbstractNode.kt b/node/src/main/kotlin/com/r3corda/node/internal/AbstractNode.kt
index 7580da60e5..1eb2ab54c1 100644
--- a/node/src/main/kotlin/com/r3corda/node/internal/AbstractNode.kt
+++ b/node/src/main/kotlin/com/r3corda/node/internal/AbstractNode.kt
@@ -114,7 +114,7 @@ abstract class AbstractNode(val configuration: NodeConfiguration, val networkMap
             return smm.add(loggerName, logic).resultFuture
         }
 
-        override fun registerProtocolInitiator(markerClass: KClass<*>, protocolFactory: (Party) -> ProtocolLogic<*>) {
+        override fun <P : ProtocolLogic<*>> registerProtocolInitiator(markerClass: KClass<out P>, protocolFactory: (Party) -> ProtocolLogic<*>) {
             require(markerClass !in protocolFactories) { "${markerClass.java.name} has already been used to register a protocol" }
             log.debug { "Registering ${markerClass.java.name}" }
             protocolFactories[markerClass.java] = protocolFactory
diff --git a/node/src/main/kotlin/com/r3corda/node/services/api/ServiceHubInternal.kt b/node/src/main/kotlin/com/r3corda/node/services/api/ServiceHubInternal.kt
index fa573b3514..86d9a1c738 100644
--- a/node/src/main/kotlin/com/r3corda/node/services/api/ServiceHubInternal.kt
+++ b/node/src/main/kotlin/com/r3corda/node/services/api/ServiceHubInternal.kt
@@ -72,15 +72,16 @@ abstract class ServiceHubInternal : ServiceHub {
 
     /**
      * Register the protocol factory we wish to use when a initiating party attempts to communicate with us. The
-     * registration is done against a marker [KClass] which is sent in the session handsake by the other party. If this
+     * registration is done against a marker [KClass] which is sent in the session handshake by the other party. If this
      * marker class has been registered then the corresponding factory will be used to create the protocol which will
      * communicate with the other side. If there is no mapping then the session attempt is rejected.
      * @param markerClass The marker [KClass] present in a session initiation attempt, which is a 1:1 mapping to a [Class]
      * using the <pre>::class</pre> construct. Any marker class can be used, with the default being the class of the initiating
      * protocol. This enables the registration to be of the form: registerProtocolInitiator(InitiatorProtocol::class, ::InitiatedProtocol)
      * @param protocolFactory The protocol factory generating the initiated protocol.
+     * @param R the return type of the protocol logic
      */
-    abstract fun registerProtocolInitiator(markerClass: KClass<*>, protocolFactory: (Party) -> ProtocolLogic<*>)
+    abstract fun <P : ProtocolLogic<*>> registerProtocolInitiator(markerClass: KClass<out P>, protocolFactory: (Party) -> ProtocolLogic<*>)
 
     /**
      * Return the protocol factory that has been registered with [markerClass], or null if no factory is found.
diff --git a/node/src/test/kotlin/com/r3corda/node/services/MockServiceHubInternal.kt b/node/src/test/kotlin/com/r3corda/node/services/MockServiceHubInternal.kt
index 657d23a79b..bb38499543 100644
--- a/node/src/test/kotlin/com/r3corda/node/services/MockServiceHubInternal.kt
+++ b/node/src/test/kotlin/com/r3corda/node/services/MockServiceHubInternal.kt
@@ -75,7 +75,7 @@ open class MockServiceHubInternal(
         return smm.add(loggerName, logic).resultFuture
     }
 
-    override fun registerProtocolInitiator(markerClass: KClass<*>, protocolFactory: (Party) -> ProtocolLogic<*>) {
+    override fun <P : ProtocolLogic<*>> registerProtocolInitiator(markerClass: KClass<out P>, protocolFactory: (Party) -> ProtocolLogic<*>) {
         protocolFactories[markerClass.java] = protocolFactory
     }
 
diff --git a/test-utils/src/main/kotlin/com/r3corda/testing/CoreTestUtils.kt b/test-utils/src/main/kotlin/com/r3corda/testing/CoreTestUtils.kt
index 6cd13f1d53..591617ca34 100644
--- a/test-utils/src/main/kotlin/com/r3corda/testing/CoreTestUtils.kt
+++ b/test-utils/src/main/kotlin/com/r3corda/testing/CoreTestUtils.kt
@@ -141,7 +141,7 @@ fun getFreeLocalPorts(hostName: String, numberToAlloc: Int): List<HostAndPort> {
  * @return Returns a [ListenableFuture] holding the single [ProtocolStateMachine] created by the request.
  */
 inline fun <R, reified P : ProtocolLogic<R>> AbstractNode.initiateSingleShotProtocol(
-        markerClass: KClass<*>,
+        markerClass: KClass<out ProtocolLogic<*>>,
         noinline protocolFactory: (Party) -> P): ListenableFuture<ProtocolStateMachine<R>> {
     services.registerProtocolInitiator(markerClass, protocolFactory)