diff --git a/book/config/_quarto-pdf.yml b/book/config/_quarto-pdf.yml
index 522f75f6c..53b1597b5 100644
--- a/book/config/_quarto-pdf.yml
+++ b/book/config/_quarto-pdf.yml
@@ -243,7 +243,7 @@ filters:
   - ../config/lua/inject_parts.lua
   - ../config/lua/inject_quizzes.lua
   - pandoc-ext/diagram
-  #- ../config/lua/inject_crossrefs.lua    # This must come before custom-numbered-blocks (relies on \ref{...})
+  - ../config/lua/inject_crossrefs.lua    # This must come before custom-numbered-blocks (relies on \ref{...})
   - custom-numbered-blocks
   - ../config/lua/margin-connections.lua  # This filter must come after custom-numbered-blocks