diff --git a/src/plugins/e-acsl/mpz.ml b/src/plugins/e-acsl/mpz.ml
index 808416c2e77ce1ca0eb47a292c3fc659b73f1e75..56b41eed465f6db5f0b80a7be6f238ff4653b3c4 100644
--- a/src/plugins/e-acsl/mpz.ml
+++ b/src/plugins/e-acsl/mpz.ml
@@ -48,7 +48,7 @@ let get_set_suffix_and_arg e =
   else
     match unrollType ty with
     | TInt(IChar, _) -> 
-      (if theMachine.char_is_unsigned then "_ui" else "_si"), [ e ]
+      (if theMachine.theMachine.char_is_unsigned then "_ui" else "_si"), [ e ]
     | TInt((IBool | IUChar | IUInt | IUShort | IULong), _) ->
       "_ui", [ e ]
     | TInt((ISChar | IShort | IInt | ILong), _) -> "_si", [ e ]