diff --git a/modules/rest-util/src/blaze/middleware/fhir/output.clj b/modules/rest-util/src/blaze/middleware/fhir/output.clj
index 7fe018bce..cef4e914a 100644
--- a/modules/rest-util/src/blaze/middleware/fhir/output.clj
+++ b/modules/rest-util/src/blaze/middleware/fhir/output.clj
@@ -32,22 +32,22 @@
   (with-open [_ (prom/timer generate-duration-seconds "json")]
     (fhir-spec/unform-json body)))
 
-(defn- generate-xml** [body]
+(defn- xml-byte-array [body]
   (let [out (ByteArrayOutputStream.)]
     (with-open [writer (io/writer out)]
       (xml/emit (fhir-spec/unform-xml body) writer))
     (.toByteArray out)))
 
-(defn- generate-xml* [body]
+(defn- generate-xml* [response]
   (try
-    (generate-xml** body)
+    (update response :body xml-byte-array)
     (catch Throwable e
-      (generate-xml** (handler-util/operation-outcome (ba/anomaly e))))))
+      (update response :body (constantly (xml-byte-array (handler-util/operation-outcome (ba/anomaly e))))))))
 
 (defn- generate-xml [response]
   (log/trace "generate XML")
   (with-open [_ (prom/timer generate-duration-seconds "xml")]
-    (update response :body generate-xml*)))
+    (generate-xml* response)))
 
 (defn- encode-response-json [{:keys [body] :as response} content-type]
   (cond-> response body (-> (update :body generate-json)