diff --git a/src/dune b/src/dune
index 8c037ca..842536a 100644
--- a/src/dune
+++ b/src/dune
@@ -8,4 +8,9 @@
  (lint
   (pps ppx_js_style -check-doc-comments))
  (preprocess
-  (pps ppx_compare ppx_hash ppx_sexp_conv ppx_sexp_value)))
+  (pps
+   -unused-code-warnings=force
+   ppx_compare
+   ppx_hash
+   ppx_sexp_conv
+   ppx_sexp_value)))