diff --git a/piwik/indico_piwik/queries/metrics.py b/piwik/indico_piwik/queries/metrics.py
index e9fbcab..62a2719 100644
--- a/piwik/indico_piwik/queries/metrics.py
+++ b/piwik/indico_piwik/queries/metrics.py
@@ -40,7 +40,6 @@ class PiwikQueryReportEventMetricDownloads(PiwikQueryReportEventMetricBase):
     def _get_per_day_results(self, results):
         hits_calendar = {}
 
-        # Piwik returns hits as a list of hits per date
         for date, hits in results.iteritems():
             day_hits = {'total': 0, 'unique': 0}
             if hits:
diff --git a/piwik/indico_piwik/queries/utils.py b/piwik/indico_piwik/queries/utils.py
index c9a427f..3ce84a9 100644
--- a/piwik/indico_piwik/queries/utils.py
+++ b/piwik/indico_piwik/queries/utils.py
@@ -10,7 +10,11 @@ def get_json_from_remote_server(func, default={}, **kwargs):
     """
     rawjson = func(**kwargs)
     try:
-        return json.loads(rawjson)
+        data = json.loads(rawjson)
+        if isinstance(data, dict) and data.get('result') == 'error':
+            current_plugin.get_logger().error('The Piwik server responded with an error: {}'.format(data['message']))
+            return {}
+        return data
     except Exception:
         current_plugin.get_logger().exception('Unable to load JSON from source {}'.format(str(rawjson)))
         return default