diff --git a/src/opnsense/service/templates/OPNsense/Proxy/squid.conf b/src/opnsense/service/templates/OPNsense/Proxy/squid.conf
index c550ffc30..4b7096518 100644
--- a/src/opnsense/service/templates/OPNsense/Proxy/squid.conf
+++ b/src/opnsense/service/templates/OPNsense/Proxy/squid.conf
@@ -246,6 +246,9 @@ icap_client_username_encode on
 {%   else %}
 icap_client_username_encode off
 {%   endif %}
+{%   if helpers.exists('OPNsense.proxy.forward.icap.UsernameHeader') and OPNsense.proxy.forward.icap.UsernameHeader != '' %}
+icap_client_username_header {{OPNsense.proxy.forward.icap.UsernameHeader}}
+{%   endif %}
 
 # preview
 {%   if helpers.exists('OPNsense.proxy.forward.icap.EnablePreview') and OPNsense.proxy.forward.icap.EnablePreview == '1' %}