diff --git a/src/aeb_fate_data.erl b/src/aeb_fate_data.erl
index 531ec9f..644d9de 100644
--- a/src/aeb_fate_data.erl
+++ b/src/aeb_fate_data.erl
@@ -216,7 +216,7 @@ format(?FATE_BITS(B)) when B < 0 ->
 format(?FATE_VARIANT(Arities, Tag, T)) ->
     ["(| ",
       lists:join("| ",
-                 [io_lib:format("~p", [Arities]),
+                 [format_arities(Arities),
                   integer_to_list(Tag) |
                   [format(make_tuple(T))]]),
      " |)"];
@@ -247,6 +247,9 @@ format_nbits(N, Acc) ->
     Bit = $1 - (N band 1),
     format_nbits(N bsr 1, [Bit|Acc]).
 
+format_arities(Arities) ->
+    ["[ ", lists:join(", ", [integer_to_list(E) || E <- Arities]), " ]"].
+
 format_list(List) ->
     ["[ ", lists:join(", ", [format(E) || E <- List]), " ]"].