diff --git a/.github/workflows/rust.yml b/.github/workflows/rust.yml
index 689d05e1..3705e6af 100644
--- a/.github/workflows/rust.yml
+++ b/.github/workflows/rust.yml
@@ -18,25 +18,26 @@ jobs:
   fmt:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
-      - uses: dtolnay/rust-toolchain@stable
-        with:
-          components: rustfmt
-      - uses: DavidAnson/markdownlint-cli2-action@v9
+      - uses: actions/checkout@v4
+      - uses: DavidAnson/markdownlint-cli2-action@v16
         with:
           globs: "exercises/**/*.md"
       - name: Run cargo fmt
-        run: |
-          cargo fmt --all -- --check
+        run: cargo fmt --all -- --check
   test:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
         os: [ubuntu-latest, windows-latest, macOS-latest]
     steps:
-      - uses: actions/checkout@v3
-      - uses: dtolnay/rust-toolchain@stable
+      - uses: actions/checkout@v4
       - uses: swatinem/rust-cache@v2
       - name: Run cargo test
-        run: |
-          cargo test
+        run: cargo test
+  dev-check:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: swatinem/rust-cache@v2
+      - name: Run rustlings dev check
+        run: cargo run -- dev check
diff --git a/.github/workflows/web.yml b/.github/workflows/web.yml
index 5d9abe4f..ec5d4462 100644
--- a/.github/workflows/web.yml
+++ b/.github/workflows/web.yml
@@ -54,10 +54,9 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       # Setup
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
         with:
           fetch-depth: 0
-      - uses: dtolnay/rust-toolchain@stable
       - uses: swatinem/rust-cache@v2
 
       # If you use any mdbook plugins, here's the place to install them!
diff --git a/solutions/12_options/options1.rs b/solutions/12_options/options1.rs
index 1ffbb045..230af3af 100644
--- a/solutions/12_options/options1.rs
+++ b/solutions/12_options/options1.rs
@@ -4,8 +4,8 @@
 // `hour_of_day` is higher than 23.
 fn maybe_icecream(hour_of_day: u16) -> Option<u16> {
     match hour_of_day {
-        0..22 => Some(5),
-        22..24 => Some(0),
+        0..=21 => Some(5),
+        22..=23 => Some(0),
         _ => None,
     }
 }