diff --git a/bramble-api/src/main/java/org/briarproject/bramble/api/sync/ClientId.java b/bramble-api/src/main/java/org/briarproject/bramble/api/sync/ClientId.java
index ee2b3b0ad9f99d61ee20ae9cd971b5c2279e4af0..9f873b8e9602d2c67b9fd773f1eed7ae790ec5dc 100644
--- a/bramble-api/src/main/java/org/briarproject/bramble/api/sync/ClientId.java
+++ b/bramble-api/src/main/java/org/briarproject/bramble/api/sync/ClientId.java
@@ -36,4 +36,8 @@ public class ClientId implements Comparable<ClientId> {
 		return id.hashCode();
 	}
 
+	@Override
+	public String toString() {
+		return id;
+	}
 }
diff --git a/briar-api/src/main/java/org/briarproject/briar/api/blog/BlogPostFactory.java b/briar-api/src/main/java/org/briarproject/briar/api/blog/BlogPostFactory.java
index 6a07a18c22f4dcee7a275e010bc598cd5d5c5a6a..9bfc80696792b2021b0455c53de49295699aba84 100644
--- a/briar-api/src/main/java/org/briarproject/briar/api/blog/BlogPostFactory.java
+++ b/briar-api/src/main/java/org/briarproject/briar/api/blog/BlogPostFactory.java
@@ -17,8 +17,8 @@ import static org.briarproject.briar.api.blog.BlogManager.CLIENT_ID;
 @NotNullByDefault
 public interface BlogPostFactory {
 
-	String SIGNING_LABEL_POST = CLIENT_ID + "/POST";
-	String SIGNING_LABEL_COMMENT = CLIENT_ID + "/COMMENT";
+	String SIGNING_LABEL_POST = CLIENT_ID.getString() + "/POST";
+	String SIGNING_LABEL_COMMENT = CLIENT_ID.getString() + "/COMMENT";
 
 	BlogPost createBlogPost(GroupId groupId, long timestamp,
 			@Nullable MessageId parent, LocalAuthor author, String body)
diff --git a/briar-api/src/main/java/org/briarproject/briar/api/forum/ForumPostFactory.java b/briar-api/src/main/java/org/briarproject/briar/api/forum/ForumPostFactory.java
index a6ff14554ebedfc8b58f9f83fc4a01083a66900c..51f47fbe5ba6b9e4d8932f479b39734d06486bfd 100644
--- a/briar-api/src/main/java/org/briarproject/briar/api/forum/ForumPostFactory.java
+++ b/briar-api/src/main/java/org/briarproject/briar/api/forum/ForumPostFactory.java
@@ -16,7 +16,7 @@ import static org.briarproject.briar.api.forum.ForumManager.CLIENT_ID;
 @NotNullByDefault
 public interface ForumPostFactory {
 
-	String SIGNING_LABEL_POST = CLIENT_ID + "/POST";
+	String SIGNING_LABEL_POST = CLIENT_ID.getString() + "/POST";
 
 	@CryptoExecutor
 	ForumPost createPost(GroupId groupId, long timestamp,
diff --git a/briar-api/src/main/java/org/briarproject/briar/api/privategroup/GroupMessageFactory.java b/briar-api/src/main/java/org/briarproject/briar/api/privategroup/GroupMessageFactory.java
index 0de8ada8730a59e6a805eee4f29bd62bd9eb15ee..a36ce0be74179549d08887474aa4d64186df9117 100644
--- a/briar-api/src/main/java/org/briarproject/briar/api/privategroup/GroupMessageFactory.java
+++ b/briar-api/src/main/java/org/briarproject/briar/api/privategroup/GroupMessageFactory.java
@@ -13,8 +13,8 @@ import static org.briarproject.briar.api.privategroup.PrivateGroupManager.CLIENT
 @NotNullByDefault
 public interface GroupMessageFactory {
 
-	String SIGNING_LABEL_JOIN = CLIENT_ID + "/JOIN";
-	String SIGNING_LABEL_POST = CLIENT_ID + "/POST";
+	String SIGNING_LABEL_JOIN = CLIENT_ID.getString() + "/JOIN";
+	String SIGNING_LABEL_POST = CLIENT_ID.getString() + "/POST";
 
 	/**
 	 * Creates a join announcement message for the creator of a group.
diff --git a/briar-api/src/main/java/org/briarproject/briar/api/privategroup/invitation/GroupInvitationFactory.java b/briar-api/src/main/java/org/briarproject/briar/api/privategroup/invitation/GroupInvitationFactory.java
index f539a04124b605dccdcd9bcb6ada2d7fc9fa1cad..a07aee2f82b25ab971fbe329a24aafe9b99daaac 100644
--- a/briar-api/src/main/java/org/briarproject/briar/api/privategroup/invitation/GroupInvitationFactory.java
+++ b/briar-api/src/main/java/org/briarproject/briar/api/privategroup/invitation/GroupInvitationFactory.java
@@ -12,7 +12,7 @@ import static org.briarproject.briar.api.privategroup.invitation.GroupInvitation
 @NotNullByDefault
 public interface GroupInvitationFactory {
 
-	String SIGNING_LABEL_INVITE = CLIENT_ID + "/INVITE";
+	String SIGNING_LABEL_INVITE = CLIENT_ID.getString() + "/INVITE";
 
 	/**
 	 * Returns a signature to include when inviting a member to join a private
diff --git a/briar-core/src/main/java/org/briarproject/briar/introduction/IntroduceeManager.java b/briar-core/src/main/java/org/briarproject/briar/introduction/IntroduceeManager.java
index f074700aef3c1ec7c9093e9155068852bf82cb64..846b8b4f6587e20624e6147ebd76358531e52caa 100644
--- a/briar-core/src/main/java/org/briarproject/briar/introduction/IntroduceeManager.java
+++ b/briar-core/src/main/java/org/briarproject/briar/introduction/IntroduceeManager.java
@@ -98,7 +98,8 @@ class IntroduceeManager {
 	private static final Logger LOG =
 			Logger.getLogger(IntroduceeManager.class.getName());
 
-	static final String SIGNING_LABEL_RESPONSE = CLIENT_ID + "/RESPONSE";
+	static final String SIGNING_LABEL_RESPONSE =
+			CLIENT_ID.getString() + "/RESPONSE";
 
 	private final MessageSender messageSender;
 	private final DatabaseComponent db;