diff --git a/mailman3/templates/core.yaml b/mailman3/templates/core.yaml
index 6456c21..ab4d873 100644
--- a/mailman3/templates/core.yaml
+++ b/mailman3/templates/core.yaml
@@ -51,7 +51,7 @@ spec:
             - name: SMTP_HOST
               value: {{ .Values.smtp.host }}
             - name: SMTP_PORT
-              value: {{ .Values.smtp.port }}
+              value: "{{ .Values.smtp.port }}"
             {{- else }}
             - name: SMTP_HOST
               value: {{ include "mailman3.fullname" . }}-core.{{ .Release.Namespace }}.svc.{{ $clusterDomain }}