diff --git a/plugins/datasource-zabbix/zabbixAPI.js b/plugins/datasource-zabbix/zabbixAPI.js
index c1ddd9c..c84d829 100644
--- a/plugins/datasource-zabbix/zabbixAPI.js
+++ b/plugins/datasource-zabbix/zabbixAPI.js
@@ -20,7 +20,7 @@ function (angular, _) {
       this.url              = api_url;
       this.username         = username;
       this.password         = password;
-      this.auth             = null;
+      this.auth             = "";
 
       this.requestOptions = {
         basicAuth: basicAuth,
@@ -38,33 +38,29 @@ function (angular, _) {
 
     p.request = function(method, params) {
       var self = this;
-      if (this.auth) {
-        return ZabbixAPIService.request(this.url, method, params, this.requestOptions, this.auth)
-          .then(function(result) {
-            return result;
-          },
+      return ZabbixAPIService.request(this.url, method, params, this.requestOptions, this.auth)
+        .then(function(result) {
+          return result;
+        },
 
-          // Handle errors
-          function(error) {
-            if (error.message === "Session terminated, re-login, please.") {
-              throw 'expired';
-              return self.login().then(function(auth) {
-                self.auth = auth;
-                return ZabbixAPIService.request(self.url, method, params, self.requestOptions, self.auth);
-              });
-            }
-          });
-      } else {
-
-        // Login first
-        //throw 'unauthenticated';
-        return self.loginOnce().then(function(auth) {
-          self.auth = auth;
-          return ZabbixAPIService.request(self.url, method, params, self.requestOptions, self.auth);
+        // Handle errors
+        function(error) {
+          if (isAuthError(error.data)) {
+            return self.loginOnce().then(function() {
+              return self.request(method, params);
+            });
+          }
         });
-      }
     };
 
+    function isAuthError(message) {
+      return (
+        message === "Session terminated, re-login, please." ||
+        message === "Not authorised." ||
+        message === "Not authorized."
+      );
+    }
+
     /**
      * When API unauthenticated or auth token expired each request produce login()
      * call. But auth token is common to all requests. This function wraps login() method
@@ -78,6 +74,7 @@ function (angular, _) {
         self.loginPromise = deferred.promise;
         self.login().then(function(auth) {
           self.loginPromise = null;
+          self.auth = auth;
           deferred.resolve(auth);
         });
       } else {
diff --git a/plugins/datasource-zabbix/zabbixAPIService.js b/plugins/datasource-zabbix/zabbixAPIService.js
index 0b12b8d..03f7789 100644
--- a/plugins/datasource-zabbix/zabbixAPIService.js
+++ b/plugins/datasource-zabbix/zabbixAPIService.js
@@ -17,6 +17,7 @@ function (angular) {
      * @return {object}  response.result
      */
     this.request = function(api_url, method, params, options, auth) {
+      var deferred = $q.defer();
       var requestData = {
         jsonrpc: '2.0',
         method: method,
@@ -24,8 +25,12 @@ function (angular) {
         id: 1
       };
 
-      // Set auth parameter only if it needed
-      if (auth) {
+      if (auth === "") {
+        // Reject immediately if not authenticated
+        deferred.reject({data: "Not authorised."});
+        return deferred.promise;
+      } else if (auth) {
+        // Set auth parameter only if it needed
         requestData.auth = auth;
       }
 
@@ -46,19 +51,20 @@ function (angular) {
         requestOptions.headers.Authorization = options.basicAuth;
       }
 
-      return backendSrv.datasourceRequest(requestOptions).then(function (response) {
+      backendSrv.datasourceRequest(requestOptions).then(function (response) {
         // General connection issues
         if (!response.data) {
-          return [];
+          deferred.reject(response);
         }
 
         // Handle Zabbix API errors
         else if (response.data.error) {
-          throw new ZabbixException(response.data.error);
+          deferred.reject(response.data.error);
         }
 
-        return response.data.result;
+        deferred.resolve(response.data.result);
       });
+      return deferred.promise;
     };
 
     /**