diff --git a/src/s2_pn_counters.erl b/src/s2_pn_counters.erl
index 275d406..16ee022 100644
--- a/src/s2_pn_counters.erl
+++ b/src/s2_pn_counters.erl
@@ -34,7 +34,7 @@
 %%%_* Code =============================================================
 %%%_ * Types -----------------------------------------------------------
 -define(M                 ,  s2_vclocks).
--opaque pn_counter()      :: {?M:new(), ?M:new()}.
+-opaque pn_counter()      :: {?M:vclock(), ?M:vclock()}.
 
 %%%_ * gen_lattice callbacks -------------------------------------------
 new()                     -> {?M:new(), ?M:new()}.
diff --git a/src/s2_util.erl b/src/s2_util.erl
index a8007dd..4d9ea7d 100644
--- a/src/s2_util.erl
+++ b/src/s2_util.erl
@@ -23,12 +23,15 @@
 
 %%%_* Exports ==========================================================
 -export([ consult_string/1
-        , init_folsom/1
         , ensure_map/1
         , report_failed/1
         , report_exception/1
         ]).
 
+-ifdef(S2_USE_FOLSOM).
+-export([init_folsom/1]).
+-endif.
+
 -ignore_xref([init_folsom/1]).
 
 %%%_* Includes =========================================================
@@ -53,6 +56,7 @@ consult_string_test() ->
   {error, _} = consult_string([12345]).
 -endif.
 
+-ifdef(S2_USE_FOLSOM).
 init_folsom(Metrics) ->
   ?lift([begin
            F = s2_atoms:catenate(['new_', Type]),
@@ -63,6 +67,7 @@ init_folsom(Metrics) ->
            folsom_metrics:tag_metric(A, {func, Func}),
            [folsom_metrics:tag_metric(A, {ret, Ret}) || Ret <- Rest]
          end || {Type, [App, Mod, Func|Rest] = Name} <- Metrics]).
+-endif.
 
 -spec ensure_map(map() | list({atom(),any()})) -> map().
 %% @doc Ensure parameters to OTP logger is a map
diff --git a/src/stdlib2.app.src b/src/stdlib2.app.src
index 3a293da..7797762 100644
--- a/src/stdlib2.app.src
+++ b/src/stdlib2.app.src
@@ -1,6 +1,6 @@
 {application, stdlib2, [ {description,  "stdlib2"}
                        , {vsn,          git}
                        , {registered,   []}
-                       , {applications, [kernel, stdlib]}
+                       , {applications, [kernel, stdlib, compiler]}
                        , {modules, []}
                        ]}.