diff --git a/src/proto_alpha/lib_protocol/test/helpers/test_tez.ml b/src/proto_alpha/lib_protocol/test/helpers/test_tez.ml
index 93296a7f0..35e7a45f6 100644
--- a/src/proto_alpha/lib_protocol/test/helpers/test_tez.ml
+++ b/src/proto_alpha/lib_protocol/test/helpers/test_tez.ml
@@ -23,7 +23,7 @@ module Tez = struct
   let ( + ) t1 t2 =
     match t1 +? t2 with
     | Ok r -> r
-    | Error r ->
+    | Error _ ->
         Pervasives.failwith "adding tez"
 
   let of_int x =