diff --git a/guix-data-service/web/server.scm b/guix-data-service/web/server.scm
index b1075a0..e453643 100644
--- a/guix-data-service/web/server.scm
+++ b/guix-data-service/web/server.scm
@@ -325,8 +325,8 @@ port. Also, the port used can be changed by passing the --port option.\n"
                                     (or (resource-pool-timeout-error? exn)
                                         (resource-pool-too-many-waiters-error? exn))))
                                (case (most-appropriate-mime-type
-                                      mime-types
-                                      '(text/html application/json))
+                                      '(text/html application/json)
+                                      mime-types)
                                  ((application/json)
                                   (apply
                                    values
diff --git a/guix-data-service/web/util.scm b/guix-data-service/web/util.scm
index 6c0caa7..79ca69a 100644
--- a/guix-data-service/web/util.scm
+++ b/guix-data-service/web/util.scm
@@ -33,8 +33,8 @@
 
             uri-encode-filename))
 
-(define (most-appropriate-mime-type accepted-mime-types
-                                    supported-mime-types)
+(define (most-appropriate-mime-type supported-mime-types
+                                    accepted-mime-types)
   (or
    ;; Pick the first supported mime-type
    (find (lambda (accepted-mime-type)