diff --git a/rally_openstack/services/grafana/grafana.py b/rally_openstack/services/grafana/grafana.py
index eb5b7664..aa0edba1 100644
--- a/rally_openstack/services/grafana/grafana.py
+++ b/rally_openstack/services/grafana/grafana.py
@@ -60,11 +60,12 @@ class GrafanaService(service.Service):
                                       self._spec["grafana"]["password"]))
             result = resp.json()
             LOG.debug("Grafana response code: %s" % resp.status_code)
-            is_result = result.get("data") or len(result["data"]["result"]) < 1
-            if is_result and i + 1 >= retries_total:
+            no_result = (result.get("data") is None or
+                         len(result["data"]["result"]) < 1)
+            if no_result and i + 1 >= retries_total:
                 LOG.debug("No instance metrics found in Grafana")
                 return False
-            elif is_result:
+            elif no_result:
                 i += 1
                 commonutils.interruptable_sleep(sleep_time)
             else: