diff --git a/.gitignore b/.gitignore
index bf027b4..cd66ac9 100644
--- a/.gitignore
+++ b/.gitignore
@@ -4,3 +4,4 @@
 /v1.5.0.tar.gz
 /v1.6.4.tar.gz
 /v1.6.5.tar.gz
+/v1.6.6.tar.gz
diff --git a/cppo-1.6.5-string-capitalize.patch b/cppo-1.6.5-string-capitalize.patch
deleted file mode 100644
index 7a4fe1d..0000000
--- a/cppo-1.6.5-string-capitalize.patch
+++ /dev/null
@@ -1,11 +0,0 @@
---- ./cppo-1.6.5/src/cppo_eval.ml.old	2019-04-29 18:27:54.177974043 +0100
-+++ ./cppo-1.6.5/src/cppo_eval.ml	2019-04-29 18:28:01.770989363 +0100
-@@ -85,7 +85,7 @@
- let trim_compact_and_capitalize_string s =
-   let buf = Buffer.create (String.length s) in
-   trim_and_compact buf s;
--  String.capitalize (Buffer.contents buf)
-+  String.capitalize_ascii (Buffer.contents buf)
- 
- let is_ident s =
-   let len = String.length s in
diff --git a/ocaml-cppo.spec b/ocaml-cppo.spec
index 1aa26d1..b5e3be1 100644
--- a/ocaml-cppo.spec
+++ b/ocaml-cppo.spec
@@ -4,16 +4,13 @@
 %endif
 
 Name:           ocaml-cppo
-Version:        1.6.5
-Release:        7%{?dist}
+Version:        1.6.6
+Release:        1%{?dist}
 Summary:        Equivalent of the C preprocessor for OCaml programs
 
 License:        BSD
 URL:            http://mjambon.com/cppo.html
-Source0:        https://github.com/mjambon/cppo/archive/v%{version}.tar.gz
-
-# Replace deprecated function String.capitalize.
-Patch1:         cppo-1.6.5-string-capitalize.patch
+Source0:        https://github.com/ocaml-community/cppo/archive/v%{version}.tar.gz
 
 BuildRequires:  ocaml >= 3.10.0
 BuildRequires:  ocaml-findlib
@@ -42,7 +39,6 @@ to the robustness of cppo across OCaml versions.
 
 %prep
 %setup -q -n %{libname}-%{version}
-%patch1 -p2
 sed -i.add-debuginfo \
     's/ocamlopt/ocamlopt -g/;s/ocamlc \(-[co]\)/ocamlc -g \1/' \
     Makefile
@@ -72,7 +68,10 @@ make test
 
 
 %changelog
-* Sun Jan 19 2020 Richard W.M. Jones <rjones@redhat.com> - 1.6.5-7
+* Sun Jan 19 2020 Richard W.M. Jones <rjones@redhat.com> - 1.6.6-1
+- New upstream version 1.6.6.
+- Change build system from jbuilder to dune.
+- Remove patch for fix which is now upstream.
 - OCaml 4.10.0+beta1 rebuild.
 
 * Fri Dec 06 2019 Richard W.M. Jones <rjones@redhat.com> - 1.6.5-6
diff --git a/sources b/sources
index 86239cb..efd6b16 100644
--- a/sources
+++ b/sources
@@ -1 +1 @@
-SHA512 (v1.6.5.tar.gz) = e7955d578c4d3d9b2a2c40691b39912ecaffe5173b90394552978836da79ae963ae202899525e366a599a35913373fd7ab584748d1fcbdc4e53a442b42603061
+SHA512 (v1.6.6.tar.gz) = 80b0d7a5f0f5b7d9d62ddfb204ebf5e3216c2926ba7f667b9ef10981de6a51cd6d670b7062769bf6fbdd163c1c8fb5426a74c31234ddc03ec94a75645bf469da