diff --git a/spectrum/src/frontends/slack/SlackUserRegistration.cpp b/spectrum/src/frontends/slack/SlackUserRegistration.cpp
index a8a9897e..b2aa4fb1 100644
--- a/spectrum/src/frontends/slack/SlackUserRegistration.cpp
+++ b/spectrum/src/frontends/slack/SlackUserRegistration.cpp
@@ -126,8 +126,17 @@ std::string SlackUserRegistration::handleOAuth2Code(const std::string &code, con
 		}
 	}
 
+	std::string domain = getTeamDomain(token);
+	if (domain.empty()) {
+		return "The token you have provided is invalid";
+	}
+
 	UserInfo user;
-	user.jid = getTeamDomain(token);
+	if (m_storageBackend->getUser(domain, user)) {
+		return "You have already registered this Spectrum 2 transport for this Slack Team";
+	}
+
+	user.jid = domain;
 	user.uin = "";
 	user.password = "";
 	user.language = "en";
diff --git a/src/SQLite3Backend.cpp b/src/SQLite3Backend.cpp
index eedbf94c..6a1b907e 100644
--- a/src/SQLite3Backend.cpp
+++ b/src/SQLite3Backend.cpp
@@ -120,7 +120,7 @@ bool SQLite3Backend::connect() {
 	if (createDatabase() == false)
 		return false;
 
-	PREP_STMT(m_setUser, "INSERT OR REPLACE INTO " + m_prefix + "users (id, jid, uin, password, language, encoding, last_login, vip) VALUES (?, ?, ?, ?, ?, ?, DATETIME('NOW'), ?)");
+	PREP_STMT(m_setUser, "INSERT OR REPLACE INTO " + m_prefix + "users (jid, uin, password, language, encoding, last_login, vip) VALUES (?, ?, ?, ?, ?, DATETIME('NOW'), ?)");
 	PREP_STMT(m_getUser, "SELECT id, jid, uin, password, encoding, language, vip FROM " + m_prefix + "users WHERE jid=?");
 
 	PREP_STMT(m_removeUser, "DELETE FROM " + m_prefix + "users WHERE id=?");
@@ -223,18 +223,12 @@ bool SQLite3Backend::exec(const std::string &query) {
 
 void SQLite3Backend::setUser(const UserInfo &user) {
 	sqlite3_reset(m_setUser);
-	if (user.id == 0) {
-		sqlite3_bind_null(m_setUser, 1);
-	}
-	else {
-		sqlite3_bind_int(m_setUser, 1, user.id);
-	}
-	sqlite3_bind_text(m_setUser, 2, user.jid.c_str(), -1, SQLITE_STATIC);
-	sqlite3_bind_text(m_setUser, 3, user.uin.c_str(), -1, SQLITE_STATIC);
-	sqlite3_bind_text(m_setUser, 4, user.password.c_str(), -1, SQLITE_STATIC);
-	sqlite3_bind_text(m_setUser, 5, user.language.c_str(), -1, SQLITE_STATIC);
-	sqlite3_bind_text(m_setUser, 6, user.encoding.c_str(), -1, SQLITE_STATIC);
-	sqlite3_bind_int (m_setUser, 7, user.vip);
+	sqlite3_bind_text(m_setUser, 1, user.jid.c_str(), -1, SQLITE_STATIC);
+	sqlite3_bind_text(m_setUser, 2, user.uin.c_str(), -1, SQLITE_STATIC);
+	sqlite3_bind_text(m_setUser, 3, user.password.c_str(), -1, SQLITE_STATIC);
+	sqlite3_bind_text(m_setUser, 4, user.language.c_str(), -1, SQLITE_STATIC);
+	sqlite3_bind_text(m_setUser, 5, user.encoding.c_str(), -1, SQLITE_STATIC);
+	sqlite3_bind_int (m_setUser, 6, user.vip);
 
 	if(sqlite3_step(m_setUser) != SQLITE_DONE) {
 		LOG4CXX_ERROR(logger, "setUser query"<< (sqlite3_errmsg(m_db) == NULL ? "" : sqlite3_errmsg(m_db)));