diff --git a/src/tools/rustbook/Cargo.lock b/src/tools/rustbook/Cargo.lock
index 3b859fe98c5..1394675a9dc 100644
--- a/src/tools/rustbook/Cargo.lock
+++ b/src/tools/rustbook/Cargo.lock
@@ -690,6 +690,7 @@ dependencies = [
  "mdbook",
  "once_cell",
  "pathdiff",
+ "pulldown-cmark",
  "regex",
  "semver",
  "serde_json",