diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 165343a..3b5d36d 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -12,14 +12,18 @@ jobs:
     strategy:
       matrix:
         pair:
+          - otp-version: '18.0'
+            elixir-version: '1.1'
+          - otp-version: '23.0'
+            elixir-version: '1.10'
           # Full Versions
-          - otp-version: 22.0
-            elixir-version: 1.9.1
+          - otp-version: '22.0'
+            elixir-version: '1.9.1'
           # Semver ranges
-          - otp-version: 21.x
-            elixir-version: <1.9.1
+          - otp-version: '21.x'
+            elixir-version: '<1.9.1'
           # Branches
-          - otp-version: 22.0
+          - otp-version: '22.0'
             elixir-version: master
     steps:
       - uses: actions/checkout@v2
diff --git a/README.md b/README.md
index 3dd87d9..f447269 100644
--- a/README.md
+++ b/README.md
@@ -21,6 +21,10 @@ For best results, we recommend specifying exact OTP and Elixir versions.
 However, values like `22.x` are also accepted, and we attempt to resolve them
 according to semantic versioning rules.
 
+Additionally, it is recommended that one specifies OTP and Elixir versions
+using YAML strings, as these examples do, so that numbers like `23.0` don't
+end up being parsed as `23`, which is not equivalent.
+
 ### Basic example
 
 ```yaml
@@ -33,8 +37,8 @@ jobs:
       - uses: actions/checkout@v2
       - uses: actions/setup-elixir@v1
         with:
-          otp-version: 22.2
-          elixir-version: 1.9.4
+          otp-version: '22.2'
+          elixir-version: '1.9.4'
       - run: mix deps.get
       - run: mix test
 ```
@@ -50,8 +54,8 @@ jobs:
     name: OTP ${{matrix.otp}} / Elixir ${{matrix.elixir}}
     strategy:
       matrix:
-        otp: [20.3, 21.3, 22.2]
-        elixir: [1.8.2, 1.9.4]
+        otp: ['20.3', '21.3', '22.2']
+        elixir: ['1.8.2', '1.9.4']
     steps:
       - uses: actions/checkout@v2
       - uses: actions/setup-elixir@v1
@@ -87,8 +91,8 @@ jobs:
       - uses: actions/checkout@v2
       - uses: actions/setup-elixir@v1
         with:
-          otp-version: 22.2
-          elixir-version: 1.9.4
+          otp-version: '22.2'
+          elixir-version: '1.9.4'
       - run: mix deps.get
       - run: mix test
 ```
diff --git a/dist/.github/workflows/test.yml b/dist/.github/workflows/test.yml
index 165343a..3b5d36d 100644
--- a/dist/.github/workflows/test.yml
+++ b/dist/.github/workflows/test.yml
@@ -12,14 +12,18 @@ jobs:
     strategy:
       matrix:
         pair:
+          - otp-version: '18.0'
+            elixir-version: '1.1'
+          - otp-version: '23.0'
+            elixir-version: '1.10'
           # Full Versions
-          - otp-version: 22.0
-            elixir-version: 1.9.1
+          - otp-version: '22.0'
+            elixir-version: '1.9.1'
           # Semver ranges
-          - otp-version: 21.x
-            elixir-version: <1.9.1
+          - otp-version: '21.x'
+            elixir-version: '<1.9.1'
           # Branches
-          - otp-version: 22.0
+          - otp-version: '22.0'
             elixir-version: master
     steps:
       - uses: actions/checkout@v2
diff --git a/test-project/mix.exs b/test-project/mix.exs
index 1f4f680..69d6504 100644
--- a/test-project/mix.exs
+++ b/test-project/mix.exs
@@ -5,7 +5,7 @@ defmodule Test.MixProject do
     [
       app: :test,
       version: "0.1.0",
-      elixir: "~> 1.9",
+      elixir: "~> 1.1",
       start_permanent: Mix.env() == :prod,
       deps: deps()
     ]