diff --git a/src/server/app.py b/src/server/app.py
index 463d4e7..493ac0e 100644
--- a/src/server/app.py
+++ b/src/server/app.py
@@ -82,7 +82,13 @@ def create_app() -> Flask:
         )
         if status == 204:
             return Response(b"", status=204, headers=headers)
-        return Response(encode_body(payload), status=status, headers=headers)
+        return Response(
+            encode_body(payload),
+            status=status,
+            headers=headers,
+            mimetype="application/json",
+            content_type="application/json",
+        )
 
     @app.route("/roster", methods=["PUT"])
     def roster_put():