diff --git a/README.md b/README.md
index c7e6281f..1e7e3a6c 100644
--- a/README.md
+++ b/README.md
@@ -378,6 +378,8 @@ The modules that ship with Scryer Prolog are also called
   write `integer_si(X)` to ensure soundness of your programs.
   "si" stands for *sufficiently instantiated*, and also for
   *sound inference*.
+* [`debug`](src/lib/debug.pl)
+  Various predicates that allow for declarative debugging.
 * [`pio`](src/lib/pio.pl)
   `phrase_from_file/2` applies a DCG nonterminal to the contents of a
   file, reading lazily only as much as is needed. Due to the compact