diff --git a/include/extensible.h b/include/extensible.h
index 7e271900d..e2299d3ce 100644
--- a/include/extensible.h
+++ b/include/extensible.h
@@ -135,6 +135,9 @@ public:
 	/** Allows extensions to access the extension store. */
 	friend class ExtensionItem;
 
+	/** The type of extensible that this is. */
+	const ExtensionType extype:2;
+
 	~Extensible() override;
 
 	/** @copydoc Cullable::Cull */
@@ -158,7 +161,7 @@ public:
 	void UnhookExtensions(const std::vector<ExtensionItem*>& items);
 
 protected:
-	Extensible();
+	Extensible(ExtensionType exttype);
 
 private:
 	/** The values for extensions which are set on this extensible. */
diff --git a/include/membership.h b/include/membership.h
index 92114b133..4a2ddd936 100644
--- a/include/membership.h
+++ b/include/membership.h
@@ -73,7 +73,12 @@ public:
 	 * Call Channel::JoinUser() or ForceJoin() to make a user join a channel instead of constructing
 	 * Membership objects directly.
 	 */
-	Membership(User* u, Channel* c) : user(u), chan(c) {}
+	Membership(User* u, Channel* c)
+		: Extensible(ExtensionType::MEMBERSHIP)
+		, user(u)
+		, chan(c)
+	{
+	}
 
 	/** Check if this member has a given prefix mode set
 	 * @param pm Prefix mode to check
diff --git a/src/channels.cpp b/src/channels.cpp
index b1d2e9822..983b89177 100644
--- a/src/channels.cpp
+++ b/src/channels.cpp
@@ -34,7 +34,8 @@ namespace
 }
 
 Channel::Channel(const std::string &cname, time_t ts)
-	: name(cname)
+	: Extensible(ExtensionType::CHANNEL)
+	, name(cname)
 	, age(ts)
 {
 	if (!ServerInstance->Channels.GetChans().emplace(cname, this).second)
diff --git a/src/extensible.cpp b/src/extensible.cpp
index 63bcec3d9..32106e030 100644
--- a/src/extensible.cpp
+++ b/src/extensible.cpp
@@ -47,8 +47,9 @@ ExtensionItem* ExtensionManager::GetItem(const std::string& name)
 	return iter->second;
 }
 
-Extensible::Extensible()
-	: culled(false)
+Extensible::Extensible(ExtensionType exttype)
+	: extype(exttype)
+	, culled(false)
 {
 }
 
diff --git a/src/modules/m_spanningtree/main.cpp b/src/modules/m_spanningtree/main.cpp
index 70005841f..98dda1800 100644
--- a/src/modules/m_spanningtree/main.cpp
+++ b/src/modules/m_spanningtree/main.cpp
@@ -851,9 +851,8 @@ void ModuleSpanningTree::OnShutdown(const std::string& reason)
 void ModuleSpanningTree::OnDecodeMetaData(Extensible* target, const std::string& extname, const std::string& extdata)
 {
 	// HACK: this should use automatically synced user metadata in v4.
-	User* dest = static_cast<User*>(target);
-	if (dest && (extname == "uniqueusername"))
-		dest->uniqueusername = (extdata != "0");
+	if (target->extype == ExtensionType::USER && irc::equals(extname, "uniqueusername"))
+		static_cast<User*>(target)->uniqueusername = (extdata != "0");
 }
 
 Cullable::Result ModuleSpanningTree::Cull()
diff --git a/src/modules/m_swhois.cpp b/src/modules/m_swhois.cpp
index f6d65cf87..9623c8fb1 100644
--- a/src/modules/m_swhois.cpp
+++ b/src/modules/m_swhois.cpp
@@ -143,9 +143,8 @@ public:
 
 	void OnDecodeMetaData(Extensible* target, const std::string& extname, const std::string&) override
 	{
-		User* dest = static_cast<User*>(target);
-		if (dest && (extname == "swhois"))
-			cmd.operblock.Unset(dest);
+		if (target->extype == ExtensionType::USER && irc::equals(extname, "swhois"))
+			cmd.operblock.Unset(static_cast<User*>(target));
 	}
 };
 
diff --git a/src/users.cpp b/src/users.cpp
index a02c3570f..0e47ff694 100644
--- a/src/users.cpp
+++ b/src/users.cpp
@@ -77,7 +77,8 @@ std::string User::GetModeLetters(bool includeparams) const
 }
 
 User::User(const std::string& uid, Server* srv, Type type)
-	: age(ServerInstance->Time())
+	: Extensible(ExtensionType::USER)
+	, age(ServerInstance->Time())
 	, uuid(uid)
 	, server(srv)
 	, registered(REG_NONE)