diff --git a/src/session/session.ml b/src/session/session.ml
index 1123875fbe89f5b42b303ee93b6c8193e4617127..a1417ffd61648847869c5abb6240ffd34c811a69 100644
--- a/src/session/session.ml
+++ b/src/session/session.ml
@@ -699,7 +699,7 @@ and save_ty fmt ty =
 
 let save_theory ctxt fmt t =
   fprintf fmt
-    "@\n@[<v 1>@[<h><theory@ %a@ sum=\"%a\"%a>@]"
+    "@\n@[<v 1>@[<h><theory@ %a%a%a>@]"
     save_ident t.theory_name
     (opt save_checksum "sum") t.theory_checksum
     (save_bool_def "expanded" false) t.theory_expanded;