diff --git a/charts/cloudnative-pg-cluster/Chart.yaml b/charts/cloudnative-pg-cluster/Chart.yaml
index b261995..ccb295d 100644
--- a/charts/cloudnative-pg-cluster/Chart.yaml
+++ b/charts/cloudnative-pg-cluster/Chart.yaml
@@ -2,7 +2,7 @@ apiVersion: v2
 name: cnpg-cluster
 description: Create postgres tenant clusters managed by the CNPG Operator
 type: application
-version: 0.3.10
+version: 0.3.11
 
 maintainers:
   - name: "cloudymax"
diff --git a/charts/cloudnative-pg-cluster/README.md b/charts/cloudnative-pg-cluster/README.md
index 127f076..54f89d4 100644
--- a/charts/cloudnative-pg-cluster/README.md
+++ b/charts/cloudnative-pg-cluster/README.md
@@ -1,6 +1,6 @@
 # cnpg-cluster
 
-![Version: 0.3.10](https://img.shields.io/badge/Version-0.3.10-informational?style=flat-square) ![Type: application](https://img.shields.io/badge/Type-application-informational?style=flat-square)
+![Version: 0.3.11](https://img.shields.io/badge/Version-0.3.11-informational?style=flat-square) ![Type: application](https://img.shields.io/badge/Type-application-informational?style=flat-square)
 
 Create postgres tenant clusters managed by the CNPG Operator
 
diff --git a/charts/cloudnative-pg-cluster/templates/user_certificates.yaml b/charts/cloudnative-pg-cluster/templates/user_certificates.yaml
index 084db65..2ddf402 100644
--- a/charts/cloudnative-pg-cluster/templates/user_certificates.yaml
+++ b/charts/cloudnative-pg-cluster/templates/user_certificates.yaml
@@ -1,19 +1,20 @@
 {{- if and .Values.certificates.user.enabled }}
 {{- range .Values.certificates.user.username }}
+{{- $username := . | replace "_" "-" -}}
 ---
 apiVersion: v1
 kind: Secret
 metadata:
-  name: "{{ $.Values.name }}-{{ . }}-cert"
+  name: "{{ $.Values.name }}-{{ $username }}-cert"
   labels:
     cnpg.io/reload: ""
 ---
 apiVersion: cert-manager.io/v1
 kind: Certificate
 metadata:
-  name: "{{ $.Values.name }}-{{ . }}-cert"
+  name: "{{ $.Values.name }}-{{ $username }}-cert"
 spec:
-  secretName: "{{ $.Values.name }}-{{ . }}-cert"
+  secretName: "{{ $.Values.name }}-{{ $username }}-cert"
   usages:
     - client auth
   commonName: {{ . }}