diff --git a/.gitignore b/.gitignore
index 5b5dfea..391eef6 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,3 @@
 /ocaml-base64-2.0.0.tar.gz
 /v2.1.2.tar.gz
+/base64-v3.4.0.tbz
diff --git a/ocaml-base64.spec b/ocaml-base64.spec
index b41d3aa..4ad42f6 100644
--- a/ocaml-base64.spec
+++ b/ocaml-base64.spec
@@ -1,21 +1,19 @@
-%global opt %(test -x %{_bindir}/ocamlopt && echo 1 || echo 0)
-%if ! %opt
+# There's a problem building the debugsource package which I don't
+# understand.  This should be solvable in future.
 %global debug_package %{nil}
-%endif
 
 Name:           ocaml-base64
-Version:        2.1.2
-Release:        31%{?dist}
+Version:        3.4.0
+Release:        1%{?dist}
 Summary:        Base64 library for OCaml
 
 License:        ISC
 URL:            https://github.com/mirage/ocaml-base64
-Source0:        https://github.com/mirage/ocaml-base64/archive/v%{version}.tar.gz
+Source0:        https://github.com/mirage/ocaml-base64/releases/download/v%{version}/base64-v%{version}.tbz
 
 BuildRequires:  ocaml
-BuildRequires:  ocaml-ocamlbuild
 BuildRequires:  ocaml-ocamldoc
-BuildRequires:  ocaml-findlib
+BuildRequires:  ocaml-dune-devel
 
 
 %description
@@ -34,33 +32,30 @@ Development files for %{name}.
 
 
 %prep
-%setup -q
+%setup -q -n base64-v%{version}
 
 
 %build
-# Bizarro build system, so build and install it by hand.
-ocamlbuild -use-ocamlfind -classic-display -tag debug src/b64.cma
-ocamlbuild -use-ocamlfind -classic-display -tag debug src/b64.cmxa
-ocamlbuild -use-ocamlfind -classic-display -tag debug src/b64.cmxs
+# Only build the source directory since the other directories
+# require packages that we don't have or need.
+rm -r fuzz test
+dune build %{?_smp_mflags}
 
 
 %install
-export DESTDIR=$RPM_BUILD_ROOT
-export OCAMLFIND_DESTDIR=$RPM_BUILD_ROOT%{_libdir}/ocaml
-mkdir -p $OCAMLFIND_DESTDIR
-sed 's/^version.*/version = "%{version}"/' < pkg/META > META
-ocamlfind install base64 _build/src/* META
+dune install --destdir=%{buildroot}
 
-# Delete a few files we don't really want.
-pushd $OCAMLFIND_DESTDIR/base64
-rm b64.annot b64.cmt b64.cmti
-popd
+# We do not want the ml files
+find %{buildroot}%{_libdir}/ocaml -name \*.ml -delete
+
+# We install the documentation with the doc macro
+rm -fr %{buildroot}%{_prefix}/doc
 
 
 %files
 %doc README.md
 %{_libdir}/ocaml/base64
-%if %opt
+%ifarch %{ocaml_native_compiler}
 %exclude %{_libdir}/ocaml/base64/*.a
 %exclude %{_libdir}/ocaml/base64/*.cmx
 %exclude %{_libdir}/ocaml/base64/*.cmxa
@@ -71,7 +66,7 @@ popd
 
 %files devel
 %doc CHANGES.md
-%if %opt
+%ifarch %{ocaml_native_compiler}
 %{_libdir}/ocaml/base64/*.a
 %{_libdir}/ocaml/base64/*.cmx
 %{_libdir}/ocaml/base64/*.cmxa
@@ -81,6 +76,10 @@ popd
 
 
 %changelog
+* Thu Jan 21 2021 Richard W.M. Jones <rjones@redhat.com> - 3.4.0-1
+- New upstream version 3.4.0.
+- Use dune to build.
+
 * Tue Sep 01 2020 Richard W.M. Jones <rjones@redhat.com> - 2.1.2-31
 - OCaml 4.11.1 rebuild
 
diff --git a/sources b/sources
index b48269f..757dc00 100644
--- a/sources
+++ b/sources
@@ -1 +1 @@
-479d28f71f28df483bf34d3a2cffaf04  v2.1.2.tar.gz
+SHA512 (base64-v3.4.0.tbz) = e66a67302a9eb136044bebf66a89a1d6e38a96c70622bb6cd27916fec36dcaf4b5b7e7d00c25608f0a2363f2ca4264a5fe765fe7747590958325dbce06311db9