diff --git a/include/extension.h b/include/extension.h
index 59ce432e6..3e7ce435c 100644
--- a/include/extension.h
+++ b/include/extension.h
@@ -48,6 +48,13 @@ public:
 	 */
 	virtual void FromNetwork(Extensible* container, const std::string& value) noexcept;
 
+	/** Called when a value for this extension is synchronised across the network.
+	 * @param container The container that this extension is set on.
+	 * @param item The value that is set on the container.
+	 * @param server The server which is being synchronised to or nullptr for a broadcast.
+	 */
+	virtual void OnSync(const Extensible* container, void* item, Server* server);
+
 	/** @copydoc ServiceProvider::RegisterService */
 	void RegisterService() override;
 
diff --git a/src/extensible.cpp b/src/extensible.cpp
index e5e1c6c96..383398fd5 100644
--- a/src/extensible.cpp
+++ b/src/extensible.cpp
@@ -96,6 +96,10 @@ ExtensionItem::ExtensionItem(Module* mod, const std::string& Key, ExtensionType
 {
 }
 
+void ExtensionItem::OnSync(const Extensible* container, void* item, Server* server)
+{
+}
+
 void ExtensionItem::RegisterService()
 {
 	if (!ServerInstance->Extensions.Register(this))
@@ -138,6 +142,7 @@ void ExtensionItem::Sync(const Extensible* container, void* item)
 	const std::string networkstr = item ? ToNetwork(container, item) : "";
 	if (!networkstr.empty())
 		ServerInstance->PI->SendMetadata(container, name, networkstr);
+	OnSync(container, item, nullptr);
 }
 
 void ExtensionItem::FromInternal(Extensible* container, const std::string& value) noexcept
diff --git a/src/modules/m_spanningtree/main.cpp b/src/modules/m_spanningtree/main.cpp
index c58004a70..37a1b36d6 100644
--- a/src/modules/m_spanningtree/main.cpp
+++ b/src/modules/m_spanningtree/main.cpp
@@ -512,7 +512,10 @@ void ModuleSpanningTree::OnUserConnect(LocalUser* user)
 	{
 		const std::string value = item->ToNetwork(user, obj);
 		if (!value.empty())
+		{
 			ServerInstance->PI->SendMetadata(user, item->name, value);
+			item->OnSync(user, obj, nullptr);
+		}
 	}
 
 	Utils->TreeRoot->UserCount++;
diff --git a/src/modules/m_spanningtree/netburst.cpp b/src/modules/m_spanningtree/netburst.cpp
index d862b48f7..48ce55176 100644
--- a/src/modules/m_spanningtree/netburst.cpp
+++ b/src/modules/m_spanningtree/netburst.cpp
@@ -242,7 +242,10 @@ void TreeSocket::SyncChannel(Channel* chan, TreeServer* s)
 	{
 		const std::string valuestr = item->ToNetwork(chan, value);
 		if (!valuestr.empty())
+		{
 			this->WriteLine(CommandMetadata::Builder(chan, item->name, valuestr));
+			item->OnSync(chan, value, s);
+		}
 	}
 
 	for (const auto& [_, memb] : chan->GetUsers())
@@ -251,7 +254,10 @@ void TreeSocket::SyncChannel(Channel* chan, TreeServer* s)
 		{
 			const std::string valuestr = item->ToNetwork(memb, value);
 			if (!valuestr.empty())
+			{
 				this->WriteLine(CommandMetadata::Builder(memb, item->name, valuestr));
+				item->OnSync(memb, value, s);
+			}
 		}
 	}
 
@@ -282,7 +288,10 @@ void TreeSocket::SendUsers(TreeServer* s)
 		{
 			const std::string value = item->ToNetwork(user, obj);
 			if (!value.empty())
+			{
 				this->WriteLine(CommandMetadata::Builder(user, item->name, value));
+				item->OnSync(user, obj, s);
+			}
 		}
 
 		Utils->Creator->synceventprov.Call(&ServerProtocol::SyncEventListener::OnSyncUser, user, *s);