diff --git a/bramble-api/src/main/java/org/briarproject/bramble/api/transport/KeyManager.java b/bramble-api/src/main/java/org/briarproject/bramble/api/transport/KeyManager.java
index 086e46416..db906e649 100644
--- a/bramble-api/src/main/java/org/briarproject/bramble/api/transport/KeyManager.java
+++ b/bramble-api/src/main/java/org/briarproject/bramble/api/transport/KeyManager.java
@@ -23,7 +23,7 @@ public interface KeyManager {
 	/**
 	 * Derives and stores a set of rotation mode transport keys for
 	 * communicating with the given contact over the given transport and
-	 * returns the key set ID.
+	 * returns the key set ID, or null if the transport is not supported.
 	 * <p/>
 	 * {@link StreamContext StreamContexts} for the contact can be created
 	 * after this method has returned.
@@ -31,6 +31,7 @@ public interface KeyManager {
 	 * @param alice True if the local party is Alice
 	 * @param active Whether the derived keys can be used for outgoing streams
 	 */
+	@Nullable
 	KeySetId addRotationKeys(Transaction txn, ContactId c, TransportId t,
 			SecretKey rootKey, long timestamp, boolean alice,
 			boolean active) throws DbException;
diff --git a/bramble-core/src/main/java/org/briarproject/bramble/transport/KeyManagerImpl.java b/bramble-core/src/main/java/org/briarproject/bramble/transport/KeyManagerImpl.java
index ded31ab50..8d6ce998c 100644
--- a/bramble-core/src/main/java/org/briarproject/bramble/transport/KeyManagerImpl.java
+++ b/bramble-core/src/main/java/org/briarproject/bramble/transport/KeyManagerImpl.java
@@ -51,7 +51,6 @@ class KeyManagerImpl implements KeyManager, Service, EventListener {
 	private final DatabaseComponent db;
 	private final Executor dbExecutor;
 	private final PluginConfig pluginConfig;
-	private final TransportKeyManagerFactory transportKeyManagerFactory;
 	private final TransportCrypto transportCrypto;
 
 	private final ConcurrentHashMap<TransportId, TransportKeyManager> managers;
@@ -61,34 +60,39 @@ class KeyManagerImpl implements KeyManager, Service, EventListener {
 	KeyManagerImpl(DatabaseComponent db,
 			@DatabaseExecutor Executor dbExecutor,
 			PluginConfig pluginConfig,
-			TransportKeyManagerFactory transportKeyManagerFactory,
-			TransportCrypto transportCrypto) {
+			TransportCrypto transportCrypto,
+			TransportKeyManagerFactory transportKeyManagerFactory) {
 		this.db = db;
 		this.dbExecutor = dbExecutor;
 		this.pluginConfig = pluginConfig;
-		this.transportKeyManagerFactory = transportKeyManagerFactory;
 		this.transportCrypto = transportCrypto;
 		managers = new ConcurrentHashMap<>();
+		for (SimplexPluginFactory f : pluginConfig.getSimplexFactories()) {
+			TransportKeyManager m = transportKeyManagerFactory.
+					createTransportKeyManager(f.getId(), f.getMaxLatency());
+			managers.put(f.getId(), m);
+		}
+		for (DuplexPluginFactory f : pluginConfig.getDuplexFactories()) {
+			TransportKeyManager m = transportKeyManagerFactory.
+					createTransportKeyManager(f.getId(), f.getMaxLatency());
+			managers.put(f.getId(), m);
+		}
 	}
 
 	@Override
 	public void startService() throws ServiceException {
 		if (used.getAndSet(true)) throw new IllegalStateException();
-		Map<TransportId, Integer> transports = new HashMap<>();
-		for (SimplexPluginFactory f : pluginConfig.getSimplexFactories())
-			transports.put(f.getId(), f.getMaxLatency());
-		for (DuplexPluginFactory f : pluginConfig.getDuplexFactories())
-			transports.put(f.getId(), f.getMaxLatency());
 		try {
 			db.transaction(false, txn -> {
-				for (Entry<TransportId, Integer> e : transports.entrySet())
-					db.addTransport(txn, e.getKey(), e.getValue());
-				for (Entry<TransportId, Integer> e : transports.entrySet()) {
-					TransportKeyManager m = transportKeyManagerFactory
-							.createTransportKeyManager(e.getKey(),
-									e.getValue());
-					managers.put(e.getKey(), m);
-					m.start(txn);
+				for (SimplexPluginFactory f :
+						pluginConfig.getSimplexFactories()) {
+					db.addTransport(txn, f.getId(), f.getMaxLatency());
+					managers.get(f.getId()).start(txn);
+				}
+				for (DuplexPluginFactory f :
+						pluginConfig.getDuplexFactories()) {
+					db.addTransport(txn, f.getId(), f.getMaxLatency());
+					managers.get(f.getId()).start(txn);
 				}
 			});
 		} catch (DbException e) {
diff --git a/bramble-core/src/test/java/org/briarproject/bramble/transport/KeyManagerImplTest.java b/bramble-core/src/test/java/org/briarproject/bramble/transport/KeyManagerImplTest.java
index 142f06538..02bb20244 100644
--- a/bramble-core/src/test/java/org/briarproject/bramble/transport/KeyManagerImplTest.java
+++ b/bramble-core/src/test/java/org/briarproject/bramble/transport/KeyManagerImplTest.java
@@ -25,6 +25,7 @@ import java.util.Collection;
 import java.util.Map;
 import java.util.Random;
 
+import static java.util.Collections.emptyList;
 import static java.util.Collections.singletonList;
 import static java.util.Collections.singletonMap;
 import static org.briarproject.bramble.api.transport.TransportConstants.TAG_LENGTH;
@@ -71,8 +72,7 @@ public class KeyManagerImplTest extends BrambleMockTestCase {
 	private final SecretKey rootKey = getSecretKey();
 	private final Random random = new Random();
 
-	private final KeyManagerImpl keyManager = new KeyManagerImpl(db, executor,
-			pluginConfig, transportKeyManagerFactory, transportCrypto);
+	private KeyManagerImpl keyManager;
 
 	@Before
 	public void testStartService() throws Exception {
@@ -83,18 +83,25 @@ public class KeyManagerImplTest extends BrambleMockTestCase {
 				singletonList(pluginFactory);
 		int maxLatency = 1337;
 
-		context.checking(new DbExpectations() {{
-			oneOf(pluginConfig).getSimplexFactories();
+		context.checking(new Expectations() {{
+			allowing(pluginConfig).getSimplexFactories();
 			will(returnValue(factories));
-			oneOf(pluginFactory).getId();
+			allowing(pluginFactory).getId();
 			will(returnValue(transportId));
-			oneOf(pluginFactory).getMaxLatency();
+			allowing(pluginFactory).getMaxLatency();
 			will(returnValue(maxLatency));
-			oneOf(db).addTransport(txn, transportId, maxLatency);
+			allowing(pluginConfig).getDuplexFactories();
+			will(returnValue(emptyList()));
 			oneOf(transportKeyManagerFactory)
 					.createTransportKeyManager(transportId, maxLatency);
 			will(returnValue(transportKeyManager));
-			oneOf(pluginConfig).getDuplexFactories();
+		}});
+
+		keyManager = new KeyManagerImpl(db, executor,
+				pluginConfig, transportCrypto, transportKeyManagerFactory);
+
+		context.checking(new DbExpectations() {{
+			oneOf(db).addTransport(txn, transportId, maxLatency);
 			oneOf(db).transaction(with(false), withDbRunnable(txn));
 			oneOf(transportKeyManager).start(txn);
 		}});