diff --git a/src/cbor/dune b/src/cbor/dune
index e6d64590..0d11d1f8 100644
--- a/src/cbor/dune
+++ b/src/cbor/dune
@@ -1,7 +1,5 @@
 (library
  (name containers_cbor)
  (libraries containers)
- (preprocess
-  (action
-   (run %{project_root}/src/core/cpp/cpp.exe %{input-file})))
+ (preprocess (pps bisect_ppx))
  (public_name containers.cbor))
diff --git a/src/core/dune b/src/core/dune
index bd362200..3d5622e7 100644
--- a/src/core/dune
+++ b/src/core/dune
@@ -3,8 +3,10 @@
  (public_name containers)
  (wrapped false)
  (preprocess
-  (action
-   (run %{project_root}/src/core/cpp/cpp.exe %{input-file})))
+  (per_module
+   ((action (run %{project_root}/src/core/cpp/cpp.exe %{input-file}))
+    CCAtomic CCList CCVector)
+   ((pps bisect_ppx))))
  (flags :standard -nolabels -open CCMonomorphic)
  (libraries either containers.monomorphic containers.domain))