diff --git a/application/CayaProtocol.h b/application/CayaProtocol.h
index 3971994..fa2899b 100644
--- a/application/CayaProtocol.h
+++ b/application/CayaProtocol.h
@@ -8,6 +8,12 @@
 
 #include <Messenger.h>
 
+// Caya protocol interface version
+#define CAYA_VERSION_1_PRE_ALPHA_1		0x00000001
+#define CAYA_VERSION_1_ALPHA_1			0x00000100
+
+#define CAYA_VERSION 					CAYA_VERSION_1_PRE_ALPHA_1
+
 class CayaProtocolMessengerInterface {
 public:
 	virtual status_t SendMessage(BMessage* message) = 0;
@@ -15,27 +21,32 @@ public:
 
 class CayaProtocol {
 public:
-	// Messenger
+	//! Messenger
 	virtual status_t Init(CayaProtocolMessengerInterface*) = 0;
 
-	// Called before unloading from memory
+	//! Called before unloading from memory
 	virtual status_t Shutdown() = 0;
 
-	// Process message
+	//! Process message
 	virtual status_t Process(BMessage*) = 0;
 
-	// Change settings
+	//! Change settings
 	virtual status_t UpdateSettings(BMessage*) = 0;
 
-	// Protocol information
+	//! Protocol signature
 	virtual const char* Signature() const = 0;
+
+	//! Protocol name
 	virtual const char* FriendlySignature() const = 0;
 
-	// Preferred encoding of messages
+	//! Preferred encoding of messages
 	virtual uint32 GetEncoding() = 0;
 
-	// Messenger interface used
+	//! Messenger interface used
 	virtual CayaProtocolMessengerInterface* MessengerInterface() const = 0;
+
+	//! Caya interface version
+	virtual uint32 Version() const = 0;
 };
 
 #endif	// _CAYA_PROTOCOL_H
diff --git a/application/ProtocolManager.cpp b/application/ProtocolManager.cpp
index c0579a9..752216e 100644
--- a/application/ProtocolManager.cpp
+++ b/application/ProtocolManager.cpp
@@ -40,10 +40,12 @@ ProtocolManager::Init(BDirectory dir, BHandler* target)
 		if (id < 0)
 			continue;
 
+		// If add-on's API version fits then load accounts...
 		CayaProtocolAddOn* addOn = new CayaProtocolAddOn(id, path.Path());
-		fAddOnMap.AddItem(addOn->Signature(), addOn);
-
-		_GetAccounts(addOn, target);
+		if (addOn->Protocol()->Version() == CAYA_VERSION) {
+			fAddOnMap.AddItem(addOn->Signature(), addOn);
+			_GetAccounts(addOn, target);
+		}
 	}
 }
 
diff --git a/protocols/aim/AIM.cpp b/protocols/aim/AIM.cpp
index bb8a5b1..8eafbe1 100644
--- a/protocols/aim/AIM.cpp
+++ b/protocols/aim/AIM.cpp
@@ -241,6 +241,13 @@ AIMProtocol::MessengerInterface() const
 }
 
 
+uint32
+AIMProtocol::Version() const
+{
+	return CAYA_VERSION_1_PRE_ALPHA_1;
+}
+
+
 status_t
 AIMProtocol::A_LogOn()
 {
diff --git a/protocols/aim/AIM.h b/protocols/aim/AIM.h
index 3ad9648..df016e3 100644
--- a/protocols/aim/AIM.h
+++ b/protocols/aim/AIM.h
@@ -33,6 +33,8 @@ public:
 	virtual	CayaProtocolMessengerInterface*
 							MessengerInterface() const;
 
+	virtual	uint32			Version() const;
+
 	static	int32			WaitForData(void*);
 
 	static	void			GotMessage(void*, char*, int, char*);