diff --git a/.github/workflows/book.yml b/.github/workflows/book.yml
index 393ae5d..4d06b70 100644
--- a/.github/workflows/book.yml
+++ b/.github/workflows/book.yml
@@ -26,12 +26,12 @@ jobs:
             ~/.cargo/bin
             ~/.cargo/registry/index
             ~/.cargo/registry/cache
-          key: ${{ runner.os }}-build-${{ env.cache-name }}-0.2 }}
+          key: ${{ runner.os }}-build-${{ env.cache-name }}-0.3 }}
 
       - 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 "^0.2" mdbook)
+          (test -x $HOME/.cargo/bin/mdbook || cargo install --vers "^0.3" mdbook)
           cargo install-update -a
 
       - name: Build book