diff --git a/core/src/main/kotlin/net/corda/core/observable/flowSafeSubscribe.kt b/core/src/main/kotlin/net/corda/core/observable/flowSafeSubscribe.kt
new file mode 100644
index 0000000000..685c251467
--- /dev/null
+++ b/core/src/main/kotlin/net/corda/core/observable/flowSafeSubscribe.kt
@@ -0,0 +1,44 @@
+package net.corda.core.observable
+
+import net.corda.core.observable.internal.FlowSafeSubscriber
+import rx.Observable
+import rx.Subscriber
+import rx.observers.SafeSubscriber
+
+/**
+ * [Observable.flowSafeSubscribe] is used to return an Observable, through which we can subscribe non unsubscribing [rx.Observer]s
+ * to the source [Observable].
+ *
+ * It unwraps an [Observer] from a [SafeSubscriber], re-wraps it with a [FlowSafeSubscriber] and then subscribes it
+ * to the source [Observable].
+ *
+ * In case we need to subscribe with a [SafeSubscriber] via [flowSafeSubscribe], we have to:
+ * 1. Declare a custom SafeSubscriber extending [SafeSubscriber].
+ * 2. Wrap with the custom SafeSubscriber the [rx.Observer] to be subscribed to the source [Observable].
+ * 3. Call [Observable.flowSafeSubscribe] with [strictMode] = false
+ * 4. Subscribe to the returned [Observable] passing in as argument the custom SafeSubscriber.
+ */
+fun <T> Observable<T>.flowSafeSubscribe(strictMode: Boolean = false): Observable<T> {
+
+    class OnFlowSafeSubscribe<T>(val source: Observable<T>): Observable.OnSubscribe<T> {
+
+        override fun call(subscriber: Subscriber<in T>) {
+            if (isSafeSubscriber(subscriber)) {
+                source.unsafeSubscribe(FlowSafeSubscriber((subscriber as SafeSubscriber).actual))
+            } else {
+                source.unsafeSubscribe(subscriber)
+            }
+        }
+
+        private fun isSafeSubscriber(subscriber: Subscriber<*>): Boolean {
+            return if (strictMode) {
+                // In strictMode mode we capture SafeSubscriber subclasses as well
+                SafeSubscriber::class.java.isAssignableFrom(subscriber::class.java)
+            } else {
+                subscriber::class == SafeSubscriber::class
+            }
+        }
+    }
+
+    return Observable.unsafeCreate(OnFlowSafeSubscribe(this))
+}
\ No newline at end of file
diff --git a/core/src/main/kotlin/net/corda/core/internal/FlowSafeSubscriber.kt b/core/src/main/kotlin/net/corda/core/observable/internal/FlowSafeSubscriber.kt
similarity index 65%
rename from core/src/main/kotlin/net/corda/core/internal/FlowSafeSubscriber.kt
rename to core/src/main/kotlin/net/corda/core/observable/internal/FlowSafeSubscriber.kt
index 8e4d641f23..7f7e71a3d1 100644
--- a/core/src/main/kotlin/net/corda/core/internal/FlowSafeSubscriber.kt
+++ b/core/src/main/kotlin/net/corda/core/observable/internal/FlowSafeSubscriber.kt
@@ -1,7 +1,6 @@
-package net.corda.core.internal
+package net.corda.core.observable.internal
 
-import rx.Observable
-import rx.Observable.unsafeCreate
+import net.corda.core.internal.VisibleForTesting
 import rx.Observer
 import rx.Subscriber
 import rx.exceptions.CompositeException
@@ -82,42 +81,4 @@ class FlowSafeSubscriber<T>(actual: Subscriber<in T>) : SafeSubscriber<T>(actual
  * the exception will be re-thrown at [Exceptions.throwOrReport].
  */
 @VisibleForTesting
-class OnNextFailedException(message: String, cause: Throwable) : OnErrorNotImplementedException(message, cause)
-
-/**
- * [Observable.flowSafeSubscribe] is used to return an Observable, through which we can subscribe non unsubscribing [rx.Observer]s
- * to the source [Observable].
- *
- * It unwraps an [Observer] from a [SafeSubscriber], re-wraps it with a [FlowSafeSubscriber] and then subscribes it
- * to the source [Observable].
- *
- * In case we need to subscribe with a [SafeSubscriber] via [flowSafeSubscribe], we have to:
- * 1. Declare a custom SafeSubscriber extending [SafeSubscriber].
- * 2. Wrap with the custom SafeSubscriber the [rx.Observer] to be subscribed to the source [Observable].
- * 3. Call [Observable.flowSafeSubscribe] with [strictMode] = false
- * 4. Subscribe to the returned [Observable] passing in as argument the custom SafeSubscriber.
- */
-fun <T> Observable<T>.flowSafeSubscribe(strictMode: Boolean = false): Observable<T> {
-
-    class OnFlowSafeSubscribe<T>(val source: Observable<T>): Observable.OnSubscribe<T> {
-
-        override fun call(subscriber: Subscriber<in T>) {
-            if (isSafeSubscriber(subscriber)) {
-                source.unsafeSubscribe(FlowSafeSubscriber((subscriber as SafeSubscriber).actual))
-            } else {
-                source.unsafeSubscribe(subscriber)
-            }
-        }
-
-        private fun isSafeSubscriber(subscriber: Subscriber<*>): Boolean {
-            return if (strictMode) {
-                // In strictMode mode we capture SafeSubscriber subclasses as well
-                SafeSubscriber::class.java.isAssignableFrom(subscriber::class.java)
-            } else {
-                subscriber::class == SafeSubscriber::class
-            }
-        }
-    }
-
-    return unsafeCreate(OnFlowSafeSubscribe(this))
-}
\ No newline at end of file
+class OnNextFailedException(message: String, cause: Throwable) : OnErrorNotImplementedException(message, cause)
\ No newline at end of file
diff --git a/node/src/main/kotlin/net/corda/node/services/vault/NodeVaultService.kt b/node/src/main/kotlin/net/corda/node/services/vault/NodeVaultService.kt
index 365a4598be..74ab36e58d 100644
--- a/node/src/main/kotlin/net/corda/node/services/vault/NodeVaultService.kt
+++ b/node/src/main/kotlin/net/corda/node/services/vault/NodeVaultService.kt
@@ -14,6 +14,7 @@ import net.corda.core.node.StatesToRecord
 import net.corda.core.node.services.*
 import net.corda.core.node.services.Vault.ConstraintInfo.Companion.constraintInfo
 import net.corda.core.node.services.vault.*
+import net.corda.core.observable.flowSafeSubscribe
 import net.corda.core.schemas.PersistentStateRef
 import net.corda.core.serialization.SingletonSerializeAsToken
 import net.corda.core.transactions.*
diff --git a/node/src/test/kotlin/net/corda/node/utilities/ObservablesTests.kt b/node/src/test/kotlin/net/corda/node/utilities/ObservablesTests.kt
index d29ce5ac9e..fc42bc3984 100644
--- a/node/src/test/kotlin/net/corda/node/utilities/ObservablesTests.kt
+++ b/node/src/test/kotlin/net/corda/node/utilities/ObservablesTests.kt
@@ -3,9 +3,9 @@ package net.corda.node.utilities
 import com.google.common.util.concurrent.SettableFuture
 import net.corda.core.internal.bufferUntilSubscribed
 import net.corda.core.internal.tee
-import net.corda.core.internal.FlowSafeSubscriber
-import net.corda.core.internal.OnNextFailedException
-import net.corda.core.internal.flowSafeSubscribe
+import net.corda.core.observable.internal.FlowSafeSubscriber
+import net.corda.core.observable.internal.OnNextFailedException
+import net.corda.core.observable.flowSafeSubscribe
 import net.corda.nodeapi.internal.persistence.*
 import net.corda.testing.internal.configureDatabase
 import net.corda.testing.node.MockServices.Companion.makeTestDataSourceProperties