diff --git a/infra/helm/big-reference/values.yaml b/infra/helm/big-reference/values.yaml
index 20e7361..3effa75 100644
--- a/infra/helm/big-reference/values.yaml
+++ b/infra/helm/big-reference/values.yaml
@@ -275,6 +275,11 @@ workloads:
       # this issuer back, which is what browser tokens carry (infra/host-browser.yml).
       KC_HOSTNAME: '{{ include "big.keycloakUrl" . }}'
       KC_HOSTNAME_BACKCHANNEL_DYNAMIC: "true"
+      # Behind a TLS proxy (keycloakUrl) the dynamic backchannel URLs — token,
+      # userinfo, certs — take their scheme from the request, which reaches Keycloak
+      # as plain http; trusting X-Forwarded-Proto keeps them https so the browser
+      # doesn't block them as mixed content. In-cluster calls send no such header.
+      KC_PROXY_HEADERS: xforwarded
     ports: [{ name: http, port: 8080 }]
     # TCP, not /health/ready on the management port: nothing here gates on realm
     # import, and a wrong health path would leave the Service with no endpoints.