diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index cdee88e..9702040 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -11,44 +11,44 @@ on:
 jobs:
   compile:
     name: Compile code
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
       - uses: erlef/setup-beam@v1
         with:
-          otp-version: '23.3.4.18'
-          rebar3-version: '3.16.1'
+          otp-version: '25.3.2.21'
+          rebar3-version: '3.24.0'
       - run: rebar3 compile
   test:
     name: Run Common Test tests
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
       - uses: erlef/setup-beam@v1
         with:
           version-type: 'strict'
-          otp-version: '23.3.4.18'
-          rebar3-version: '3.16.1'
+          otp-version: '25.3.2.21'
+          rebar3-version: '3.24.0'
       - run: rebar3 ct
   dialyzer:
     name: Run Dialyzer
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
       - uses: erlef/setup-beam@v1
         with:
           version-type: 'strict'
-          otp-version: '23.3.4.18'
-          rebar3-version: '3.16.1'
+          otp-version: '25.3.2.21'
+          rebar3-version: '3.24.0'
       - run: rebar3 dialyzer
   lint:
     name: Run elvis linting
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
       - uses: erlef/setup-beam@v1
         with:
           version-type: 'strict'
-          otp-version: '23.3.4.18'
-          rebar3-version: '3.16.1'
+          otp-version: '25.3.2.21'
+          rebar3-version: '3.24.0'
       - run: rebar3 lint
diff --git a/.tool-versions b/.tool-versions
index d3f76b6..1d134ea 100644
--- a/.tool-versions
+++ b/.tool-versions
@@ -1,2 +1,2 @@
-erlang 23.2.4
-rebar 3.16.1
+erlang 25.3.2.21
+rebar 3.24.0
diff --git a/rebar.config b/rebar.config
index 723a6ab..9cf4a06 100644
--- a/rebar.config
+++ b/rebar.config
@@ -1,6 +1,6 @@
 {erl_opts, [debug_info]}.
 {project_plugins, [
-                   {rebar3_lint, "2.0.0"},
+                   {rebar3_lint, "3.2.6"},
                    {rebar3_hex, "7.0.2"}
                   ]}.
 {deps, [
diff --git a/src/eflambe.erl b/src/eflambe.erl
index 18ea084..288e0dd 100644
--- a/src/eflambe.erl
+++ b/src/eflambe.erl
@@ -22,6 +22,8 @@
 
 -type capture_return() :: {ok, [any()]} | {error, already_mecked}.
 
+-export_type([mfa_fun/0, options/0, capture_return/0]).
+
 -define(DEFAULT_OPTIONS, [{output_format, brendan_gregg}]).
 -define(DEFAULT_APPLY_OPTIONS, [{return, value}|?DEFAULT_OPTIONS]).
 -define(DEFAULT_CAPTURE_OPTIONS, [{return, filename}|?DEFAULT_OPTIONS]).
diff --git a/src/eflambe_server.erl b/src/eflambe_server.erl
index 72d6f6f..5bd2166 100644
--- a/src/eflambe_server.erl
+++ b/src/eflambe_server.erl
@@ -24,7 +24,7 @@
                 timestamp, set_on_spawn]).
 
 -record(state, {
-          callback :: {pid(), reference()},
+          callback :: {pid(), gen_server:reply_tag()},
           module :: atom(),
           max_calls :: integer(),
           calls = 0 :: integer(),
@@ -44,12 +44,13 @@
           tracer_pid :: pid()
          }).
 
--type state() :: #state{}.
--type pid_trace() :: #pid_trace{}.
+-opaque state() :: #state{}.
+-opaque pid_trace() :: #pid_trace{}.
 -type from() :: {pid(), Tag :: term()}.
-
 -type tracer_options() :: [eflambe:option() | {pid, pid()} | {max_calls, pos_integer()}].
 
+-export_type([state/0, pid_trace/0, from/0, tracer_options/0]).
+
 %%%===================================================================
 %%% API
 %%%===================================================================
diff --git a/src/eflambe_tracer.erl b/src/eflambe_tracer.erl
index 22132ed..1fb73be 100644
--- a/src/eflambe_tracer.erl
+++ b/src/eflambe_tracer.erl
@@ -35,11 +35,12 @@
           return :: atom()
          }).
 
--type state() :: #state{}.
+-opaque state() :: #state{}.
 -type from() :: {pid(), Tag :: term()}.
-
 -type tracer_options() :: [eflambe:option() | {pid, pid()}].
 
+-export_type([state/0, from/0, tracer_options/0]).
+
 %%%===================================================================
 %%% API
 %%%===================================================================