diff --git a/src/core/core-chat-room.cpp b/src/core/core-chat-room.cpp
index 5d8c8b6e4..76bdcda8f 100644
--- a/src/core/core-chat-room.cpp
+++ b/src/core/core-chat-room.cpp
@@ -23,6 +23,7 @@
 #include "chat/chat-room/basic-chat-room.h"
 #include "chat/chat-room/chat-room-p.h"
 #include "chat/chat-room/real-time-text-chat-room.h"
+#include "conference/participant.h"
 #include "core-p.h"
 #include "logger/logger.h"
 
@@ -127,6 +128,22 @@ list<shared_ptr<ChatRoom>> Core::findChatRooms (const IdentityAddress &peerAddre
 	return output;
 }
 
+shared_ptr<ChatRoom> Core::findOneToOneChatRoom (
+	const IdentityAddress &localAddress,
+	const IdentityAddress &participantAddress
+) {
+	L_D();
+	for (const auto &chatRoom : d->chatRooms) {
+		if (
+			chatRoom->getNbParticipants() == 1 &&
+			chatRoom->getLocalAddress() == localAddress &&
+			participantAddress == chatRoom->getParticipants().front()->getAddress()
+		)
+			return chatRoom;
+	}
+	return nullptr;
+}
+
 shared_ptr<ChatRoom> Core::createClientGroupChatRoom (const string &subject) {
 	L_D();
 	return L_GET_CPP_PTR_FROM_C_OBJECT(
diff --git a/src/core/core.h b/src/core/core.h
index 9aeab7697..f88c7251d 100644
--- a/src/core/core.h
+++ b/src/core/core.h
@@ -70,6 +70,11 @@ public:
 	std::shared_ptr<ChatRoom> findChatRoom (const ChatRoomId &chatRoomId) const;
 	std::list<std::shared_ptr<ChatRoom>> findChatRooms (const IdentityAddress &peerAddress) const;
 
+	std::shared_ptr<ChatRoom> findOneToOneChatRoom (
+		const IdentityAddress &localAddress,
+		const IdentityAddress &participantAddress
+	);
+
 	std::shared_ptr<ChatRoom> createClientGroupChatRoom (const std::string &subject);
 	std::shared_ptr<ChatRoom> createClientGroupChatRoom (const std::string &subject, const IdentityAddress &localAddress);
 
diff --git a/src/db/main-db.cpp b/src/db/main-db.cpp
index a73b10b9a..fd55723f6 100644
--- a/src/db/main-db.cpp
+++ b/src/db/main-db.cpp
@@ -897,7 +897,7 @@ MainDb::MainDb (const shared_ptr<Core> &core) : AbstractDb(*new MainDbPrivate),
 			// Chatroom subject.
 			"  subject VARCHAR(255),"
 
-			"  last_notify_id INT UNSIGNED,"
+			"  last_notify_id INT UNSIGNED DEFAULT 0,"
 
 			"  flags INT UNSIGNED DEFAULT 0,"