diff --git a/src/haz3lschool/dune b/src/haz3lschool/dune
index d9c50213a5..a9f7575c78 100644
--- a/src/haz3lschool/dune
+++ b/src/haz3lschool/dune
@@ -13,3 +13,11 @@
  (libraries ppx_yojson_conv.expander haz3lcore haz3lschool)
  (preprocess
   (pps ppx_yojson_conv ppx_let ppx_sexp_conv ppx_deriving.show)))
+
+(env
+ (dev
+  (js_of_ocaml
+   (flags :standard --debuginfo --noinline --dynlink --linkall --sourcemap)))
+ (release
+  (js_of_ocaml
+   (flags :standard))))
diff --git a/src/pretty/dune b/src/pretty/dune
index 8ad0954572..868d03defc 100644
--- a/src/pretty/dune
+++ b/src/pretty/dune
@@ -5,3 +5,11 @@
  (libraries util sexplib)
  (preprocess
   (pps ppx_let ppx_sexp_conv)))
+
+(env
+ (dev
+  (js_of_ocaml
+   (flags :standard --debuginfo --noinline --dynlink --linkall --sourcemap)))
+ (release
+  (js_of_ocaml
+   (flags :standard))))