diff --git a/.github/dependabot.yml b/.github/dependabot.yml
new file mode 100644
index 0000000..5ace460
--- /dev/null
+++ b/.github/dependabot.yml
@@ -0,0 +1,6 @@
+version: 2
+updates:
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "weekly"
diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index da1c522..7532cdd 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -8,22 +8,25 @@ on:
     branches:
       - 'main'
 
+permissions:
+  contents: read
+
 jobs:
   build:
     name: Test on OTP ${{ matrix.otp_version }} and ${{ matrix.os }}
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        otp_version: ['26.0', '25.2.3', '24.1.2', '23.3']
-        rebar3_version: ['3.20.0']
-        os: [ubuntu-20.04]
+        otp_version: ['28', '27', '26']
+        rebar3_version: ['3.27.0']
+        os: [ubuntu-24.04]
     env:
       OTP_VERSION: ${{ matrix.otp_version }}
 
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
 
-    - uses: erlef/setup-beam@v1
+    - uses: erlef/setup-beam@fc68ffb90438ef2936bbb3251622353b3dcb2f93 # v1.24.0
       with:
         otp-version: ${{ matrix.otp_version }}
         rebar3-version: ${{ matrix.rebar3_version }}
@@ -34,19 +37,19 @@ jobs:
       run: rebar3 ct --cover
     - name: Covertool
       run: rebar3 covertool generate
-    - uses: codecov/codecov-action@v2
+    - uses: codecov/codecov-action@e79a6962e0d4c0c17b229090214935d2e33f8354 # v6.0.1
       if: ${{ always() }}
       with:
-        file: _build/test/covertool/grpcbox.covertool.xml
+        files: _build/test/covertool/grpcbox.covertool.xml
         env_vars: OTP_VERSION
 
     - name: Setup Go 1.21.4
-      uses: actions/setup-go@v4
+      uses: actions/setup-go@4a3601121dd01d1626a1e23e37211e3254c1c06c # v6.4.0
       with:
         # Semantic version range syntax or exact version of Go
         go-version: '1.21.4'
 
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
       with:
         repository: 'grpc/grpc-go'
         path: 'grpc-go'
@@ -68,17 +71,16 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        otp_version: ['26.0']
-        rebar3_version: ['3.22.1']
-        os: [ubuntu-20.04]
+        otp_version: ['28']
+        rebar3_version: ['3.27.0']
+        os: [ubuntu-24.04]
     steps:
-    - uses: actions/checkout@v2
-    - uses: erlef/setup-beam@v1
+    - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+    - uses: erlef/setup-beam@fc68ffb90438ef2936bbb3251622353b3dcb2f93 # v1.24.0
       with:
         otp-version: ${{ matrix.otp_version }}
         rebar3-version: ${{ matrix.rebar3_version }}
-        version-type: 'strict'
-    - uses: actions/cache@v2
+    - uses: actions/cache@27d5ce7f107fe9357f9df03efb73ab90386fccae # v5.0.5
       name: Cache
       with:
         path: |
diff --git a/src/grpcbox_channel.erl b/src/grpcbox_channel.erl
index 2c4781f..0656f65 100644
--- a/src/grpcbox_channel.erl
+++ b/src/grpcbox_channel.erl
@@ -46,7 +46,7 @@
                                  stream_interceptor => grpcbox_client:stream_interceptor()}
                              | undefined,
                stats_handler :: module() | undefined,
-               refresh_interval :: timer:time()}).
+               refresh_interval :: timer:time() | undefined}).
 
 -spec start_link(name(), [endpoint()], options()) -> {ok, pid()} | ignore | {error, term()}.
 start_link(Name, Endpoints, Options) ->
diff --git a/src/grpcbox_subchannel.erl b/src/grpcbox_subchannel.erl
index 02c589f..c7c2e42 100644
--- a/src/grpcbox_subchannel.erl
+++ b/src/grpcbox_subchannel.erl
@@ -25,7 +25,7 @@
                         },
                conn :: h2_stream_set:stream_set() | undefined,
                conn_pid :: pid() | undefined,
-               idle_interval :: timer:time()}).
+               idle_interval :: timer:time() | undefined}).
 
 start_link(Name, Channel, Endpoint, Encoding, StatsHandler) ->
     gen_statem:start_link(?MODULE, [Name, Channel, Endpoint, Encoding, StatsHandler], []).