diff --git a/install/scripts/install_ocaml.sh b/install/scripts/install_ocaml.sh
index fc31495..5718ed3 100755
--- a/install/scripts/install_ocaml.sh
+++ b/install/scripts/install_ocaml.sh
@@ -4,7 +4,7 @@ set -u
 set -e
 
 cd .. ; QMCCHEM_PATH="$PWD" ; cd -
-PACKAGES="core cryptokit ocamlfind sexplib pa_sexp_conv"
+PACKAGES="core cryptokit ocamlfind sexplib" # ppx_sexp_conv"
 
 declare -i i
 i=$(gcc -dumpversion | cut -d '.' -f 2)
diff --git a/ocaml/build.ninja b/ocaml/build.ninja
index 23814ba..8238517 100644
--- a/ocaml/build.ninja
+++ b/ocaml/build.ninja
@@ -1,7 +1,8 @@
 MAIN=qmcchem
 # Main program to build
 
-PACKAGES=-package core,pa_sexp_conv,cryptokit,str,ZMQ
+PACKAGES=-package core,cryptokit,str,ZMQ,sexplib.syntax
+#,ppx_sexp_conv
 # Required opam packages, for example:
 # PACKAGES=-package core,sexplib.syntax