diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index beeac13..25bafad 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -5,21 +5,28 @@ on:
     branches: [main]
   pull_request:
 
-env:
-  OTP-VERSION: 25.2.3
-  REBAR3-VERSION: 3.20.0
-
 jobs:
   check:
     runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        combo:
+        - otp-version: '25.2'
+          rebar3-version: '3.23.0'
+        - otp-version: '26.2'
+          rebar3-version: '3.23.0'
+        - otp-version: '27.2'
+          rebar3-version: '3.24.0'
+        - otp-version: '28.0'
+          rebar3-version: '3.25.0'
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
-      - uses: erlef/setup-beam@v1
+      - uses: erlef/setup-beam@v1.18
         with:
-          otp-version: ${{ env.OTP-VERSION }}
-          rebar3-version: ${{ env.REBAR3-VERSION }}
+          otp-version: ${{ matrix.combo.otp-version }}
+          rebar3-version: ${{ matrix.combo.rebar3-version }}
 
       - uses: actions/cache@v4
         id: rebar3-cache
@@ -27,7 +34,7 @@ jobs:
           path: |
             ~/.cache/rebar3
             _build
-          key: ${{ runner.os }}-${{ env.OTP-VERSION }}-${{ env.REBAR3-VERSION }}-${{ hashFiles('rebar.lock') }}
+          key: ${{ runner.os }}-${{ runner.arch }}-${{ matrix.combo.otp-version }}-${{ matrix.combo.rebar3-version }}-${{ hashFiles('rebar.lock') }}
 
       - name: Compile
         run: |
diff --git a/rebar.config b/rebar.config
index 8297b6b..1fb4c0e 100644
--- a/rebar.config
+++ b/rebar.config
@@ -5,12 +5,12 @@
 
 {deps, [
     {elli, {git, "https://github.com/elli-lib/elli.git", {branch, "main"}}},
-    {ndto, {git, "https://github.com/nomasystems/ndto.git", {tag, "0.3.1"}}},
-    {njson, {git, "https://github.com/nomasystems/njson.git", {tag, "2.0.0"}}}
+    {ndto, {git, "https://github.com/nomasystems/ndto.git", {branch, "main"}}},
+    {njson, {git, "https://github.com/nomasystems/njson.git", {branch, "main"}}}
 ]}.
 
 {plugins, [
-    {rebar3_ndto, {git, "https://github.com/nomasystems/rebar3_ndto.git", {tag, "0.3.1"}}}
+    {rebar3_ndto, {git, "https://github.com/nomasystems/rebar3_ndto.git", {branch, "main"}}}
 ]}.
 {ndto, [
     {specs, [
@@ -27,7 +27,7 @@
 
 {project_plugins, [
     erlfmt,
-    {gradualizer, {git, "https://github.com/josefs/Gradualizer.git", {tag, "0.3.0"}}},
+    gradualizer,
     rebar3_ex_doc
 ]}.
 {erlfmt, [write]}.
@@ -82,6 +82,10 @@
     erf_static
 ]}.
 
+{dialyzer, [
+    {warnings, [no_unknown]}
+]}.
+
 {xref_ignores, [
     erf,
     {erf_http_server, start_link, 4},
diff --git a/rebar.lock b/rebar.lock
index dbc5a56..689c23a 100644
--- a/rebar.lock
+++ b/rebar.lock
@@ -1,16 +1,16 @@
 [{<<"elli">>,
   {git,"https://github.com/elli-lib/elli.git",
-       {ref,"3ec352293ef493c142767127f4113c85541c32cc"}},
+       {ref,"c874c42b5d5c1fb7477bc1655134d1de9cbe0223"}},
   0},
  {<<"ncalendar">>,
   {git,"https://github.com/nomasystems/ncalendar.git",
-       {ref,"aa5615f6723585e45e82fa5524cb976cdfe3d7f7"}},
+       {ref,"3a36a9cfe85da197f5032ce9e4c0a4a4dea9e38e"}},
   1},
  {<<"ndto">>,
   {git,"https://github.com/nomasystems/ndto.git",
-       {ref,"295281b72ea4ac85e7c4d5ca42337c68b1aac137"}},
+       {ref,"e90a034e0a76deec775abdded2951adbaa54258f"}},
   0},
  {<<"njson">>,
   {git,"https://github.com/nomasystems/njson.git",
-       {ref,"94c586b92a7e24c403089cdbe2994b7e7c87b9cc"}},
+       {ref,"42ce1fb20f43d50b5b5fdec1f3265b79c51fb632"}},
   0}].
diff --git a/src/erf.erl b/src/erf.erl
index 14e8c4a..ba37463 100644
--- a/src/erf.erl
+++ b/src/erf.erl
@@ -90,7 +90,7 @@
     Headers :: [header()],
     Body :: body() | {file, binary()}
 }.
--type route_patterns() :: [{Route :: binary(), RouteRegEx :: re:mp()}].
+-type route_patterns() :: [{Route :: binary(), RouteRegEx :: binary()}].
 -type static_dir() :: {dir, binary()}.
 -type static_file() :: {file, binary()}.
 -type static_route() :: {Path :: binary(), Resource :: static_file() | static_dir()}.
@@ -427,7 +427,7 @@ route_patterns(API, StaticRoutes, SwaggerUI) ->
 
 -spec route_patterns(RawRoutes, Acc) -> RoutePatterns when
     RawRoutes :: [binary()],
-    Acc :: list(),
+    Acc :: route_patterns(),
     RoutePatterns :: route_patterns().
 route_patterns([], Acc) ->
     Acc;
diff --git a/src/erf_parser/erf_parser_oas_3_0.erl b/src/erf_parser/erf_parser_oas_3_0.erl
index 7a4143f..29706ef 100644
--- a/src/erf_parser/erf_parser_oas_3_0.erl
+++ b/src/erf_parser/erf_parser_oas_3_0.erl
@@ -483,12 +483,10 @@ parse_response(_Response, CTX) ->
     Reason :: term().
 parse_spec(SpecPath) ->
     case file:read_file(SpecPath) of
-        {ok, BinSpec} ->
+        {ok, BinSpec} when is_binary(BinSpec), byte_size(BinSpec) > 0 ->
             case filename:extension(SpecPath) of
                 JSON when JSON =:= <<".json">> orelse JSON =:= ".json" ->
                     case njson:decode(BinSpec) of
-                        {ok, undefined} ->
-                            {error, {invalid_spec, BinSpec}};
                         {ok, Spec} ->
                             {ok, Spec};
                         {error, Reason} ->
@@ -497,6 +495,8 @@ parse_spec(SpecPath) ->
                 Extension ->
                     {error, {unsupported_extension, Extension}}
             end;
+        {ok, EmptyBinSpec} ->
+            {error, {invalid_spec, EmptyBinSpec}};
         {error, Reason} ->
             {error, {invalid_spec, Reason}}
     end.
diff --git a/test/erf_SUITE.erl b/test/erf_SUITE.erl
index f219f96..c4c07fa 100644
--- a/test/erf_SUITE.erl
+++ b/test/erf_SUITE.erl
@@ -83,7 +83,7 @@ foo(_Conf) ->
 
     {ok, _Pid} = erf:start_link(#{
         spec_path => filename:join(
-            code:lib_dir(erf, test), <<"fixtures/with_refs_oas_3_0_spec.json">>
+            [code:lib_dir(erf), "test", <<"fixtures/with_refs_oas_3_0_spec.json">>]
         ),
         callback => erf_callback,
         port => 8789,
@@ -363,7 +363,7 @@ middlewares(_Conf) ->
 
     {ok, _Pid} = erf:start_link(#{
         spec_path => filename:join(
-            code:lib_dir(erf, test), <<"fixtures/with_refs_oas_3_0_spec.json">>
+            [code:lib_dir(erf), "test", <<"fixtures/with_refs_oas_3_0_spec.json">>]
         ),
         preprocess_middlewares => [erf_preprocess_middleware, erf_preprocess_stop_middleware],
         callback => erf_callback,
@@ -412,16 +412,16 @@ middlewares(_Conf) ->
 statics(_Conf) ->
     {ok, _Pid} = erf:start_link(#{
         spec_path => filename:join(
-            code:lib_dir(erf, test), <<"fixtures/with_refs_oas_3_0_spec.json">>
+            [code:lib_dir(erf), "test", <<"fixtures/with_refs_oas_3_0_spec.json">>]
         ),
         callback => erf_callback,
         port => 8789,
         static_routes => [
-            {<<"/static">>, {dir, filename:join(code:lib_dir(erf, test), <<"fixtures">>)}},
+            {<<"/static">>, {dir, filename:join([code:lib_dir(erf), "test", <<"fixtures">>])}},
             {<<"/common">>,
                 {file,
                     filename:join(
-                        code:lib_dir(erf, test), <<"fixtures/common_oas_3_0_spec.json">>
+                        [code:lib_dir(erf), "test", <<"fixtures/common_oas_3_0_spec.json">>]
                     )}}
         ],
         name => erf_server
@@ -429,7 +429,7 @@ statics(_Conf) ->
 
     {ok, Common} = file:read_file(
         filename:join(
-            code:lib_dir(erf, test), <<"fixtures/common_oas_3_0_spec.json">>
+            [code:lib_dir(erf), "test", <<"fixtures/common_oas_3_0_spec.json">>]
         )
     ),
 
@@ -499,7 +499,7 @@ swagger_ui(_Conf) ->
 start_stop(_Conf) ->
     {ok, Pid} = erf:start_link(#{
         spec_path => filename:join(
-            code:lib_dir(erf, test), <<"fixtures/with_refs_oas_3_0_spec.json">>
+            [code:lib_dir(erf), "test", <<"fixtures/with_refs_oas_3_0_spec.json">>]
         ),
         callback => erf_callback,
         port => 8789,
@@ -542,7 +542,7 @@ reload_conf(_Conf) ->
 
     {ok, _Pid} = erf:start_link(#{
         spec_path => filename:join(
-            code:lib_dir(erf, test), <<"fixtures/with_refs_oas_3_0_spec.json">>
+            [code:lib_dir(erf), "test", <<"fixtures/with_refs_oas_3_0_spec.json">>]
         ),
         callback => erf_callback,
         port => 8789,
diff --git a/test/erf_parser_oas_3_0_SUITE.erl b/test/erf_parser_oas_3_0_SUITE.erl
index 3cecea1..b38ff9d 100644
--- a/test/erf_parser_oas_3_0_SUITE.erl
+++ b/test/erf_parser_oas_3_0_SUITE.erl
@@ -239,7 +239,7 @@ petstore(_Conf) ->
 
 with_refs(_Conf) ->
     WithRefsOAS = unicode:characters_to_binary(
-        code:lib_dir(erf, test) ++ "/fixtures/with_refs_oas_3_0_spec.json"
+        code:lib_dir(erf) ++ "/test" ++ "/fixtures/with_refs_oas_3_0_spec.json"
     ),
 
     {ok, WithRefsAPI} = erf_parser:parse(WithRefsOAS, erf_parser_oas_3_0),
@@ -271,7 +271,7 @@ with_refs(_Conf) ->
 
 invalid(_Conf) ->
     Invalid = unicode:characters_to_binary(
-        code:lib_dir(erf, test) ++ "/fixtures/invalid_oas_3_0_spec.json"
+        code:lib_dir(erf) ++ "/test" ++ "/fixtures/invalid_oas_3_0_spec.json"
     ),
 
     ?assertMatch(