diff --git a/src/tests/basic.drup.expected b/src/tests/basic.drup.expected
index fd1bf485..c4e4ad5d 100644
--- a/src/tests/basic.drup.expected
+++ b/src/tests/basic.drup.expected
@@ -9,3 +9,4 @@ i 1 -2 -4 0
 r -4 -1 0
 r -1 0
 r -3 0
+r 0
diff --git a/src/util/Util.mli b/src/util/Util.mli
index fc3a58aa..6a357e46 100644
--- a/src/util/Util.mli
+++ b/src/util/Util.mli
@@ -30,3 +30,5 @@ val setup_gc : unit -> unit
 module Int_set : CCSet.S with type elt = int
 module Int_map : CCMap.S with type key = int
 module Int_tbl : CCHashtbl.S with type key = int
+
+module Str_tbl : CCHashtbl.S with type key = string