diff --git a/ceph/meta/prometheus.yml b/ceph/meta/prometheus.yml
index 62f1b9d..4993289 100644
--- a/ceph/meta/prometheus.yml
+++ b/ceph/meta/prometheus.yml
@@ -92,7 +92,7 @@
     CephPool{{pool_name|replace(".", "")|replace("-", "")}}SpaceUsageCritical:
       {%- set threshold = monitoring_pool.pool_space_used_critical_threshold|default('0.85')|float %}
       if: >-
-        ceph_pool_usage_bytes_used{name="{{pool_name}}"} / ceph_pool_usage_max_avail{name="{{pool_name}}"} + ceph_pool_usage_bytes_used{name="{{pool_name}}"}) > {{threshold}}
+        ceph_pool_usage_bytes_used{name="{{pool_name}}"} / (ceph_pool_usage_max_avail{name="{{pool_name}}"} + ceph_pool_usage_bytes_used{name="{{pool_name}}"}) > {{threshold}}
       for: 3m
       labels:
         severity: minor