diff --git a/.github/workflows/book.yml b/.github/workflows/book.yml
index 623b90422..03e6db3bc 100644
--- a/.github/workflows/book.yml
+++ b/.github/workflows/book.yml
@@ -23,14 +23,14 @@ jobs:
             - name: Install Rust (nightly)
               uses: actions-rs/toolchain@v1
               with:
-                toolchain: nightly
+                toolchain: nightly-2024-04-05
                 components: rustfmt, clippy
                 override: true
 
             - name: Install Rust (wasm32)
               uses: actions-rs/toolchain@v1
               with:
-                toolchain: nightly
+                toolchain: nightly-2024-04-05
                 target: wasm32-unknown-unknown
                 override: true
 
@@ -56,7 +56,7 @@ jobs:
                 git config --local user.email "41898282+github-actions[bot]@users.noreply.github.com"
                 git config --local user.name "bookworm"
                 cd doc
-                make github
+                make CARGO="cargo +nightly-2024-04-05" github
                 git checkout gh-pages
 
             - name: Push changes
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 177dd0415..264f4807a 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -13,11 +13,11 @@ jobs:
       - uses: actions/checkout@v4
       - uses: actions-rs/toolchain@v1
         with:
-          toolchain: nightly
+          toolchain: nightly-2024-04-05
           override: true
       - uses: actions-rs/toolchain@v1
         with:
-          toolchain: nightly
+          toolchain: nightly-2024-04-05
           target: wasm32-unknown-unknown
           override: true
 
@@ -34,11 +34,11 @@ jobs:
 
       - name: Run test units
         run: |
-          make test
+          make CARGO="cargo +nightly-2024-04-05" test
 
       - name: Compile all bins
         run: |
-          make
+          make CARGO="cargo +nightly-2024-04-05"
 
   feature-powerset:
     name: Test crate feature powerset on ${{ matrix.os }}
@@ -51,11 +51,11 @@ jobs:
       - uses: actions/checkout@v4
       - uses: actions-rs/toolchain@v1
         with:
-          toolchain: nightly
+          toolchain: nightly-2024-04-05
           override: true
       - uses: actions-rs/toolchain@v1
         with:
-          toolchain: nightly
+          toolchain: nightly-2024-04-05
           target: wasm32-unknown-unknown
           override: true
       - uses: taiki-e/install-action@cargo-hack
@@ -72,7 +72,7 @@ jobs:
 
       - name: Run feature powerset builds
         run: |
-          make check
+          make CARGO="cargo +nightly-2024-04-05" check
 
   fmt:
     name: rustfmt
@@ -82,8 +82,8 @@ jobs:
       - uses: actions/checkout@v4
       - uses: actions-rs/toolchain@v1
         with:
-          toolchain: nightly
+          toolchain: nightly-2024-04-05
           components: rustfmt
           override: true
       - run: |
-          cargo +nightly fmt -- --check
+          cargo +nightly-2024-04-05 fmt -- --check
diff --git a/README.md b/README.md
index 47f2aebe6..dc2ecbe8a 100644
--- a/README.md
+++ b/README.md
@@ -106,7 +106,7 @@ nightly version, which was known to work:
 Now we can use that toolchain in `make` directly:
 
 ```shell
-% make CARGO="cargo +nightly-2024-02-01" {target}
+% make CARGO="cargo +nightly-2024-04-05" {target}
 ```
 
 Or, if we are lazy, we can modify the `Makefile` to always use that: