diff --git a/.github/workflows/book.yml b/.github/workflows/book.yml
index 4d06b70..2266adc 100644
--- a/.github/workflows/book.yml
+++ b/.github/workflows/book.yml
@@ -31,7 +31,7 @@ jobs:
       - name: Install mdbook
         run: |
           (test -x $HOME/.cargo/bin/cargo-install-update || cargo install cargo-update)
-          (test -x $HOME/.cargo/bin/mdbook || cargo install --vers "^0.3" mdbook)
+          (test -x $HOME/.cargo/bin/mdbook || cargo install --vers "^0.4" mdbook)
           cargo install-update -a
 
       - name: Build book