diff --git a/pkgs/by-name/cl/cld2/package.nix b/pkgs/by-name/cl/cld2/package.nix
new file mode 100644
index 00000000000000..bf28b160f2bab7
--- /dev/null
+++ b/pkgs/by-name/cl/cld2/package.nix
@@ -0,0 +1,50 @@
+{ lib
+, stdenv
+, fetchFromGitHub
+, cmake
+, fetchpatch
+}:
+
+stdenv.mkDerivation {
+  pname = "cld2";
+  version = "unstable-2015-08-21";
+
+  src = fetchFromGitHub {
+    owner = "CLD2Owners";
+    repo = "cld2";
+    rev = "b56fa78a2fe44ac2851bae5bf4f4693a0644da7b";
+    hash = "sha256-YhXs45IbriKWKULguZM4DgfV/Fzr73VHxA1pFTXCyv8=";
+  };
+
+  patches = [
+    (fetchpatch {
+      name = "add-cmakelists.txt";
+      url = "https://github.com/CLD2Owners/cld2/pull/65/commits/9cfac02c2ac7802ab7079560b38a474473c45f51.patch";
+      hash = "sha256-uOjmUk8kMFl+wED44ErXoLRyblhgDwFx9K1Wj65Omh8=";
+    })
+  ];
+
+  nativeBuildInputs = [ cmake ];
+
+  meta = with lib; {
+    homepage = "https://github.com/CLD2Owners/cld2";
+    description = "Compact Language Detector 2";
+    longDescription = ''
+      CLD2 probabilistically detects over 80 languages in Unicode UTF-8 text,
+      either plain text or HTML/XML. Legacy encodings must be converted to valid
+      UTF-8 by the caller. For mixed-language input, CLD2 returns the top three
+      languages found and their approximate percentages of the total text bytes
+      (e.g. 80% English and 20% French out of 1000 bytes of text means about 800
+      bytes of English and 200 bytes of French). Optionally, it also returns a
+      vector of text spans with the language of each identified. This may be
+      useful for applying different spelling-correction dictionaries or
+      different machine translation requests to each span. The design target is
+      web pages of at least 200 characters (about two sentences); CLD2 is not
+      designed to do well on very short text, lists of proper names, part
+      numbers, etc.
+    '';
+    license = licenses.asl20;
+    maintainers = with maintainers; [ chvp ];
+    platforms = platforms.all;
+  };
+}
diff --git a/pkgs/tools/networking/mu/default.nix b/pkgs/tools/networking/mu/default.nix
index 6f3f556e259287..46519c730446b9 100644
--- a/pkgs/tools/networking/mu/default.nix
+++ b/pkgs/tools/networking/mu/default.nix
@@ -1,21 +1,23 @@
 { lib
 , stdenv
 , fetchFromGitHub
+, glibcLocales
 , meson
 , ninja
 , pkg-config
+, python3
+, cld2
 , coreutils
 , emacs
 , glib
 , gmime3
 , texinfo
 , xapian
-, fetchpatch
 }:
 
 stdenv.mkDerivation rec {
   pname = "mu";
-  version = "1.10.8";
+  version = "1.12.0";
 
   outputs = [ "out" "mu4e" ];
 
@@ -23,23 +25,17 @@ stdenv.mkDerivation rec {
     owner = "djcb";
     repo = "mu";
     rev = "v${version}";
-    hash = "sha256-cDfW0yXA+0fZY5lv4XCHWu+5B0svpMeVMf8ttX/z4Og=";
+    hash = "sha256-z0sHDZlhsSeIf+ZRCni3j/DbfYrmn6bvYmKpt4PA2i8=";
   };
 
-  patches = [
-    (fetchpatch {
-      name = "add-mu4e-pkg.el";
-      url = "https://github.com/djcb/mu/commit/00f7053d51105eea0c72151f1a8cf0b6d8478e4e.patch";
-      hash = "sha256-21c7djmYTcqyyygqByo9vu/GsH8WMYcq8NOAvJsS5AQ=";
-    })
-  ];
-
   postPatch = ''
-    # Fix mu4e-builddir (set it to $out)
-    substituteInPlace mu4e/mu4e-config.el.in \
-      --replace "@abs_top_builddir@" "$out"
-    substituteInPlace lib/utils/mu-test-utils.cc \
-      --replace "/bin/rm" "${coreutils}/bin/rm"
+    substituteInPlace lib/utils/mu-utils-file.cc \
+      --replace-fail "/bin/rm" "${coreutils}/bin/rm"
+    substituteInPlace lib/tests/bench-indexer.cc \
+      --replace-fail "/bin/rm" "${coreutils}/bin/rm"
+    substituteInPlace lib/mu-maildir.cc \
+      --replace-fail "/bin/mv" "${coreutils}/bin/mv"
+    patchShebangs build-aux/date.py
   '';
 
   postInstall = ''
@@ -61,7 +57,7 @@ stdenv.mkDerivation rec {
     fi
   '';
 
-  buildInputs = [ emacs glib gmime3 texinfo xapian ];
+  buildInputs = [ cld2 emacs glib gmime3 texinfo xapian ];
 
   mesonFlags = [
     "-Dguile=disabled"
@@ -69,10 +65,13 @@ stdenv.mkDerivation rec {
     "-Dlispdir=${placeholder "mu4e"}/share/emacs/site-lisp"
   ];
 
-  nativeBuildInputs = [ pkg-config meson ninja ];
+  nativeBuildInputs = [ pkg-config meson ninja python3 glibcLocales ];
 
   doCheck = true;
 
+  # Tests need a UTF-8 aware locale configured
+  env.LANG = "C.UTF-8";
+
   meta = with lib; {
     description = "A collection of utilities for indexing and searching Maildirs";
     license = licenses.gpl3Plus;