diff --git a/site-modules/profile/manifests/swh/deploy/rpc_server.pp b/site-modules/profile/manifests/swh/deploy/rpc_server.pp
--- a/site-modules/profile/manifests/swh/deploy/rpc_server.pp
+++ b/site-modules/profile/manifests/swh/deploy/rpc_server.pp
@@ -116,6 +116,7 @@
       http_vhost   => '127.0.0.1',
       http_port    => $backend_listen_port,
       http_uri     => '/',
+      http_header => ['Accept: application/json'],
       http_string  => $http_check_string,
     },
     target           => $icinga_checks_file,
@@ -132,6 +133,7 @@
         http_vhost  => $::swh_hostname['internal_fqdn'],
         http_port   => $backend_listen_port,
         http_uri    => '/',
+        http_header => ['Accept: application/json'],
         http_string => $http_check_string,
       },
       target        => $icinga_checks_file,