diff --git a/libtransport/OAuth2.cpp b/libtransport/OAuth2.cpp
index bdbb56a8..6b3841c7 100644
--- a/libtransport/OAuth2.cpp
+++ b/libtransport/OAuth2.cpp
@@ -84,15 +84,27 @@ std::string OAuth2::requestToken(const std::string &code, std::string &token) {
 	rapidjson::Document resp;
 	HTTPRequest req(HTTPRequest::Get, url);
 	if (!req.execute(resp)) {
+		LOG4CXX_ERROR(logger, url);
+		LOG4CXX_ERROR(logger, req.getError());
 		return req.getError();
 	}
 
 	rapidjson::Value& access_token = resp["access_token"];
 	if (!access_token.IsString()) {
+		LOG4CXX_ERROR(logger, "No 'access_token' object in the reply.");
+		LOG4CXX_ERROR(logger, url);
+		LOG4CXX_ERROR(logger, req.getRawData());
 		return "No 'access_token' object in the reply.";
 	}
 
 	token = access_token.GetString();
+	if (token.empty()) {
+		LOG4CXX_ERROR(logger, "Empty 'access_token' object in the reply.");
+		LOG4CXX_ERROR(logger, url);
+		LOG4CXX_ERROR(logger, req.getRawData());
+		return "Empty 'access_token' object in the reply.";
+	}
+
 	return "";
 }
 
diff --git a/spectrum/src/frontends/slack/SlackUserRegistration.cpp b/spectrum/src/frontends/slack/SlackUserRegistration.cpp
index d5d868bf..60134dbc 100644
--- a/spectrum/src/frontends/slack/SlackUserRegistration.cpp
+++ b/spectrum/src/frontends/slack/SlackUserRegistration.cpp
@@ -62,7 +62,7 @@ SlackUserRegistration::~SlackUserRegistration(){
 }
 
 std::string SlackUserRegistration::createOAuth2URL(const std::vector<std::string> &args) {
-	std::string redirect_url = "http://slack.spectrum.im/oauth2/" + CONFIG_STRING(m_config, "service.jid");
+	std::string redirect_url = "https://slack.spectrum.im/oauth2/" + CONFIG_STRING(m_config, "service.jid");
 	OAuth2 *oauth2 = new OAuth2(CONFIG_STRING_DEFAULTED(m_config, "service.client_id",""),
 						  CONFIG_STRING_DEFAULTED(m_config, "service.client_secret",""),
 						  "https://slack.com/oauth/authorize",