diff --git a/api/FHIRApiService/services/base.service.js b/api/FHIRApiService/services/base.service.js
index f95ae23f..b155beb1 100644
--- a/api/FHIRApiService/services/base.service.js
+++ b/api/FHIRApiService/services/base.service.js
@@ -55,7 +55,7 @@ class BaseFhirApiService {
                 code: 409,
                 msg: handleError.duplicate(err.message)
             };
-        } else if (err.stack.includes("ValidationError")) {
+        } else if (err?.stack?.includes("ValidationError")) {
 
             let operationOutcomeError = new OperationOutcome([]);
             for (let errorKey in err.errors) {
@@ -70,7 +70,7 @@ class BaseFhirApiService {
                 msg: operationOutcomeError
             };
 
-        } else if (err.stack.includes("stored by resource")) {
+        } else if (err?.stack?.includes("stored by resource")) {
             operationOutcomeMessage = {
                 code: 400,
                 msg: handleError.processing(err.message)
@@ -91,14 +91,16 @@ class BaseFhirApiService {
             item = handleError.processing(item);
         }
 
-        if (this.response.getHeader("content-type").includes("xml") ||
-            this.request.get("accept").includes("xml")
+        if ((this.response.getHeader("content-type").includes("xml") ||
+            this.request.get("accept").includes("xml")) ||
+            this.response.locals?._format?.toLowerCase() === "xml"
         ) {
             let fhir = new FHIR();
             let xmlItem = fhir.objToXml(item);
             if (this._pretty) xmlItem = xmlFormatter(xmlItem);
             return this.response.status(code).send(xmlItem);
         }
+        
         return this.response.status(code).send(item);
     }
 
diff --git a/routes.js b/routes.js
index f071c683..b1c32219 100644
--- a/routes.js
+++ b/routes.js
@@ -12,6 +12,11 @@ if (fs.existsSync(path.join(__dirname, "./plugins/config.js"))) {
     pluginsConfig = require("./plugins/config.template").pluginsConfig;
 }
 
+/**
+ * 
+ * @param {import("express").Request} req 
+ * @param {import("express").Response} res 
+ */
 function setFormatWhenQuery(req, res) {
     let format = _.get(req, "query._format");
     if (format && format.includes("xml")) {
@@ -19,6 +24,7 @@ function setFormatWhenQuery(req, res) {
     } else if (format && format.includes("json")) {
         res.set("Content-Type", "application/fhir+json");
     }
+    res.locals._format = format;
     delete req["query"]["_format"];
 }