diff --git a/.github/workflows/on-push.yml b/.github/workflows/on-push.yml
index 9342c959..8a9766b5 100644
--- a/.github/workflows/on-push.yml
+++ b/.github/workflows/on-push.yml
@@ -9,8 +9,8 @@ jobs:
     runs-on: ubuntu-20.04
     strategy:
       matrix:
-        otp: ["23.3.4.6"]
-        elixir: ["1.10.4", "1.11.4", "1.12.3", "1.13.4", "1.14.2"]
+        otp: ["24"]
+        elixir: ["1.11", "1.12", "1.13", "1.14", "1.15"]
     steps:
       - uses: actions/checkout@v2
       - uses: erlef/setup-beam@v1
@@ -25,7 +25,7 @@ jobs:
       - run: mix deps.get
       - run: mix compile
       - run: mix format --check-formatted
-        if: matrix.elixir == '1.14.2' # Only check formatting with the latest verison
+        if: matrix.elixir == '1.15' # Only check formatting with the latest verison
       - run: mix dialyzer
-        if: matrix.elixir == '1.14.2'
+        if: matrix.elixir == '1.15'
       - run: mix test
diff --git a/.tool-versions b/.tool-versions
index 8e408b44..19876365 100644
--- a/.tool-versions
+++ b/.tool-versions
@@ -1 +1 @@
-elixir 1.14.2
+elixir 1.15
diff --git a/config/test.exs b/config/test.exs
index dd8b3653..d20c287c 100644
--- a/config/test.exs
+++ b/config/test.exs
@@ -4,8 +4,8 @@ config :logger, level: :warn
 
 config :ex_aws,
   json_codec: Test.JSONCodec,
-  access_key_id: ["test_key_id"],
-  secret_access_key: ["secret_access_key"]
+  access_key_id: "testkeyid",
+  secret_access_key: "secretaccesskey"
 
 config :ex_aws, :kinesis,
   scheme: "https://",
diff --git a/lib/ex_aws/utils.ex b/lib/ex_aws/utils.ex
index dceeb8b4..a9a179ed 100644
--- a/lib/ex_aws/utils.ex
+++ b/lib/ex_aws/utils.ex
@@ -41,7 +41,7 @@ defmodule ExAws.Utils do
   def camelize(string) do
     string
     |> to_charlist
-    |> Enum.reduce({true, ''}, fn
+    |> Enum.reduce({true, ~c""}, fn
       ?_, {_, acc} -> {true, acc}
       ?/, {_, acc} -> {false, [?. | acc]}
       char, {false, acc} -> {false, [char | acc]}
diff --git a/mix.exs b/mix.exs
index 31c19e47..2a82c349 100644
--- a/mix.exs
+++ b/mix.exs
@@ -8,7 +8,7 @@ defmodule ExAws.Mixfile do
     [
       app: :ex_aws,
       version: @version,
-      elixir: "~> 1.10",
+      elixir: "~> 1.11",
       elixirc_paths: elixirc_paths(Mix.env()),
       description: "Generic AWS client",
       name: "ExAws",