diff --git a/CHANGELOG.md b/CHANGELOG.md
index c20969f9..26735c9a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -14,6 +14,7 @@
   - Cortex / Queries: added "Lazy loaded index-headers" and "Index-header lazy load duration"
   - Cortex / Compactor: added "Tenants compaction progress"
   - Alerts: added "CortexMemoryMapAreasTooHigh"
+* [BUGFIX] Fixed workingset memory panel while rolling out a StatefulSet. #229
 
 ## 1.5.0 / 2020-11-12
 
diff --git a/cortex-mixin/dashboards/dashboard-utils.libsonnet b/cortex-mixin/dashboards/dashboard-utils.libsonnet
index e9824dea..5644af34 100644
--- a/cortex-mixin/dashboards/dashboard-utils.libsonnet
+++ b/cortex-mixin/dashboards/dashboard-utils.libsonnet
@@ -136,7 +136,9 @@ local utils = import 'mixin-utils/utils.libsonnet';
   containerMemoryWorkingSetPanel(title, containerName)::
     $.panel(title) +
     $.queryPanel([
-      'sum by(pod) (container_memory_working_set_bytes{%s,container="%s"})' % [$.namespaceMatcher(), containerName],
+      // We use "max" instead of "sum" otherwise during a rolling update of a statefulset we will end up
+      // summing the memory of the old pod (whose metric will be stale for 5m) to the new pod.
+      'max by(pod) (container_memory_working_set_bytes{%s,container="%s"})' % [$.namespaceMatcher(), containerName],
       'min(container_spec_memory_limit_bytes{%s,container="%s"} > 0)' % [$.namespaceMatcher(), containerName],
     ], ['{{pod}}', 'limit']) +
     {