diff --git a/collectd/files/plugin/collectd_openstack.py b/collectd/files/plugin/collectd_openstack.py
index 5539338..955d780 100644
--- a/collectd/files/plugin/collectd_openstack.py
+++ b/collectd/files/plugin/collectd_openstack.py
@@ -345,5 +345,9 @@
         counts = defaultdict(int)
         for obj in list_object:
             s = group_by_func(obj)
-            counts[s] += count_func(obj) if count_func else 1
+            try:
+                counts[s] += count_func(obj) if count_func else 1
+            except TypeError:
+                # Ignore when count_func() doesn't return a number
+                pass
         return counts