diff --git a/src/memtrace/dune b/src/memtrace/dune
index 7f941802..14f504c4 100644
--- a/src/memtrace/dune
+++ b/src/memtrace/dune
@@ -1,6 +1,7 @@
 (library
  (name sidekick_memtrace)
  (public_name sidekick.memtrace)
+ (synopsis "optional interface to memtrace")
  (libraries
   (select
    sidekick_memtrace.ml
diff --git a/src/zarith/dune b/src/zarith/dune
index e5147828..dc584fce 100644
--- a/src/zarith/dune
+++ b/src/zarith/dune
@@ -1,6 +1,7 @@
 (library
  (name sidekick_zarith)
  (public_name sidekick.zarith)
+ (synopsis "Interface to zarith (optional) for arithmetic")
  (optional) ; dep on zarith
  (flags :standard -warn-error -a+8)
  (libraries sidekick.core sidekick.arith zarith))