diff --git a/core/src/main/kotlin/net/corda/core/messaging/FlowHandle.kt b/core/src/main/kotlin/net/corda/core/messaging/FlowHandle.kt
index 3d75d64ca1..4c558d9767 100644
--- a/core/src/main/kotlin/net/corda/core/messaging/FlowHandle.kt
+++ b/core/src/main/kotlin/net/corda/core/messaging/FlowHandle.kt
@@ -2,6 +2,7 @@ package net.corda.core.messaging
 
 import com.google.common.util.concurrent.ListenableFuture
 import net.corda.core.flows.StateMachineRunId
+import net.corda.core.serialization.CordaSerializable
 import rx.Observable
 
 /**
@@ -23,3 +24,37 @@ interface FlowHandle<A> : AutoCloseable {
 interface FlowProgressHandle<A> : FlowHandle<A> {
     val progress: Observable<String>
 }
+
+
+@CordaSerializable
+data class FlowHandleImpl<A>(
+    override val id: StateMachineRunId,
+    override val returnValue: ListenableFuture<A>) : FlowHandle<A> {
+
+     // Remember to add @Throws to FlowHandle.close() if this throws an exception.
+    override fun close() {
+        returnValue.cancel(false)
+    }
+}
+
+@CordaSerializable
+data class FlowProgressHandleImpl<A>(
+    override val id: StateMachineRunId,
+    override val returnValue: ListenableFuture<A>,
+    override val progress: Observable<String>) : FlowProgressHandle<A> {
+
+    // Remember to add @Throws to FlowProgressHandle.close() if this throws an exception.
+    override fun close() {
+        progress.notUsed()
+        returnValue.cancel(false)
+    }
+}
+
+// Private copy of the version in client:rpc.
+private fun <T> Observable<T>.notUsed() {
+    try {
+        this.subscribe({}, {}).unsubscribe()
+    } catch (e: Exception) {
+        // Swallow any other exceptions as well.
+    }
+}
diff --git a/node/src/main/kotlin/net/corda/node/services/statemachine/FlowStateMachineImpl.kt b/node/src/main/kotlin/net/corda/node/services/statemachine/FlowStateMachineImpl.kt
index 00a89df830..1ba95a4bdd 100644
--- a/node/src/main/kotlin/net/corda/node/services/statemachine/FlowStateMachineImpl.kt
+++ b/node/src/main/kotlin/net/corda/node/services/statemachine/FlowStateMachineImpl.kt
@@ -6,7 +6,6 @@ import co.paralleluniverse.fibers.Suspendable
 import co.paralleluniverse.strands.Strand
 import com.google.common.util.concurrent.ListenableFuture
 import com.google.common.util.concurrent.SettableFuture
-import net.corda.client.rpc.notUsed
 import net.corda.core.abbreviate
 import net.corda.core.crypto.Party
 import net.corda.core.crypto.SecureHash
@@ -16,9 +15,9 @@ import net.corda.core.flows.FlowLogic
 import net.corda.core.flows.FlowStateMachine
 import net.corda.core.flows.StateMachineRunId
 import net.corda.core.messaging.FlowHandle
-import net.corda.core.messaging.FlowProgressHandle
+import net.corda.core.messaging.FlowHandleImpl
+import net.corda.core.messaging.FlowProgressHandleImpl
 import net.corda.core.random63BitValue
-import net.corda.core.serialization.CordaSerializable
 import net.corda.core.transactions.SignedTransaction
 import net.corda.core.utilities.ProgressTracker
 import net.corda.core.utilities.UntrustworthyData
@@ -430,35 +429,3 @@ class FlowStateMachineImpl<R>(override val id: StateMachineRunId,
         timer.update(duration, TimeUnit.NANOSECONDS)
     }
 }
-
-// I would prefer for [FlowProgressHandleImpl] to extend [FlowHandleImpl],
-// but Kotlin doesn't allow this for data classes, not even to create
-// another data class!
-@CordaSerializable
-private data class FlowHandleImpl<A>(
-        override val id: StateMachineRunId,
-        override val returnValue: ListenableFuture<A>) : FlowHandle<A> {
-
-    /**
-     * Use this function for flows whose returnValue is not going to be used, so as to free up server resources.
-     */
-    override fun close() {
-        returnValue.cancel(false)
-    }
-}
-
-@CordaSerializable
-private data class FlowProgressHandleImpl<A> (
-        override val id: StateMachineRunId,
-        override val returnValue: ListenableFuture<A>,
-        override val progress: Observable<String>) : FlowProgressHandle<A> {
-
-    /**
-     * Use this function for flows whose returnValue and progress are not going to be used or tracked, so as to free up server resources.
-     * Note that it won't really close if one subscribes on progress [Observable], but then forgets to unsubscribe.
-     */
-    override fun close() {
-        progress.notUsed()
-        returnValue.cancel(false)
-    }
-}