diff --git a/dune-project b/dune-project
index 29650972..a0c17c59 100644
--- a/dune-project
+++ b/dune-project
@@ -24,6 +24,7 @@
   (qcheck-core (and :with-test (>= 0.19)))
   (thread-local-storage (and (>= 0.2) (< 0.3)))
   (odoc :with-doc)
+  (hmap :with-test)
   picos
   (mdx
    (and
diff --git a/moonpool.opam b/moonpool.opam
index 001afec5..e9411025 100644
--- a/moonpool.opam
+++ b/moonpool.opam
@@ -17,6 +17,7 @@ depends: [
   "qcheck-core" {with-test & >= "0.19"}
   "thread-local-storage" {>= "0.2" & < "0.3"}
   "odoc" {with-doc}
+  "hmap" {with-test}
   "picos"
   "mdx" {>= "1.9.0" & with-test}
 ]