diff --git a/backend/src/server/plugins.ts b/backend/src/server/plugins.ts
index 5436d595b..948f9ae1c 100644
--- a/backend/src/server/plugins.ts
+++ b/backend/src/server/plugins.ts
@@ -8,7 +8,11 @@ const plugins = [
         willSendResponse(requestContext: any) {
           const { setHeaders = [] } = requestContext.context
           setHeaders.forEach(({ key, value }: { [key: string]: string }) => {
-            requestContext.response.http.headers.append(key, value)
+            if (requestContext.response.http.headers.get(key)) {
+              requestContext.response.http.headers.set(key, value)
+            } else {
+              requestContext.response.http.headers.append(key, value)
+            }
           })
           return requestContext
         },