diff --git a/collects/handin-server/main.rkt b/collects/handin-server/main.rkt
index 6b02469325..2054d7b14e 100644
--- a/collects/handin-server/main.rkt
+++ b/collects/handin-server/main.rkt
@@ -282,7 +282,8 @@
   (parameterize ([current-directory submission-dir])
     (define magics '(#"WXME"
                      #"<<<MULTI-SUBMISSION-FILE>>>"
-                     #"#reader(lib\"read.(?:rkt|ss)\"\"wxme\")WXME"))
+                     #"#reader(lib\"read.ss\"\"wxme\")WXME"
+                     #"#reader(lib\"read.rkt\"\"wxme\")WXME"))
     (define mlen (apply max (map bytes-length magics)))
     (define file
       ;; find the newest wxme file