diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 75d68e9c..65366382 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -12,13 +12,11 @@ jobs:
     name: Tests on OTP ${{matrix.otp}} with rebar v${{matrix.rebar3}}
     strategy:
       matrix:
-        otp: ['24.1.2', '23.3.4.7', '22.3.4.22']
-        rebar3: ['3.17.0']
-        include:
-          - otp: '21.3.8.24'
-            rebar3: '3.15.1'
+        otp: ['26', '25']
+        rebar3: ['3.23.0']
+
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - uses: erlef/setup-beam@v1
         with:
           otp-version: ${{matrix.otp}}
diff --git a/src/syn_backbone.erl b/src/syn_backbone.erl
index e8799330..dc5bdbe2 100755
--- a/src/syn_backbone.erl
+++ b/src/syn_backbone.erl
@@ -162,7 +162,7 @@ code_change(_OldVsn, State, _Extra) ->
 %% ===================================================================
 %% Internal
 %% ===================================================================
--spec ensure_table_existence(Type :: ets:type(), TableId :: atom(), Scope :: atom()) -> any().
+-spec ensure_table_existence(Type :: ets:table_type(), TableId :: atom(), Scope :: atom()) -> any().
 ensure_table_existence(Type, TableId, Scope) ->
     %% build name
     TableIdBin = list_to_binary(atom_to_list(TableId)),
diff --git a/src/syn_pg.erl b/src/syn_pg.erl
index 00783298..66b5a169 100644
--- a/src/syn_pg.erl
+++ b/src/syn_pg.erl
@@ -747,7 +747,7 @@ multi_call_and_receive(CollectorPid, Pid, Meta, Message, Timeout) ->
         CollectorPid ! {syn_bad_reply, Pid}
     end.
 
--spec collect_replies(MembersOD :: orddict:orddict({pid(), Meta :: term()})) ->
+-spec collect_replies(MembersOD :: orddict:orddict(pid(), Meta :: term())) ->
     {
         Replies :: [{{pid(), Meta :: term()}, Reply :: term()}],
         BadReplies :: [{pid(), Meta :: term()}]
@@ -756,7 +756,7 @@ collect_replies(MembersOD) ->
     collect_replies(MembersOD, [], []).
 
 -spec collect_replies(
-    MembersOD :: orddict:orddict({pid(), Meta :: term()}),
+    MembersOD :: orddict:orddict(pid(), Meta :: term()),
     Replies :: [{{pid(), Meta :: term()}, Reply :: term()}],
     BadReplies :: [{pid(), Meta :: term()}]
 ) ->