diff --git a/lib/attrsets.nix b/lib/attrsets.nix
index 686e125f100c..539eeb7b1721 100644
--- a/lib/attrsets.nix
+++ b/lib/attrsets.nix
@@ -455,7 +455,7 @@ rec {
   getDev = getOutput "dev";
 
   /* Pick the outputs of packages to place in buildInputs */
-  chooseDevOutputs = drvs: builtins.map (drv: if drv.outputUnspecified or false then drv.dev or drv else drv) drvs;
+  chooseDevOutputs = drvs: builtins.map getDev drvs;
 
   /*** deprecated stuff ***/
 
diff --git a/pkgs/development/libraries/libarchive/default.nix b/pkgs/development/libraries/libarchive/default.nix
index 0c5f900dd412..34ad2532d41d 100644
--- a/pkgs/development/libraries/libarchive/default.nix
+++ b/pkgs/development/libraries/libarchive/default.nix
@@ -1,5 +1,12 @@
-{ fetchurl, stdenv, acl, openssl, libxml2, attr, zlib, bzip2, e2fsprogs, xz, lzo
-, sharutils }:
+{
+  fetchurl, stdenv, pkgconfig,
+  acl, attr, bzip2, e2fsprogs, libxml2, lzo, openssl, sharutils, xz, zlib,
+
+  # Optional but increases closure only negligibly.
+  xarSupport ? true,
+}:
+
+assert xarSupport -> libxml2 != null;
 
 stdenv.mkDerivation rec {
   name = "libarchive-${version}";
@@ -10,12 +17,16 @@ stdenv.mkDerivation rec {
     sha256 = "1lngng84k1kkljl74q0cdqc3s82vn2kimfm02dgm4d6m7x71mvkj";
   };
 
-  buildInputs = [ sharutils libxml2 zlib bzip2 openssl xz lzo ] ++
-    stdenv.lib.optionals stdenv.isLinux [ e2fsprogs attr acl ];
+  nativeBuildInputs = [ pkgconfig ];
+  buildInputs = [ sharutils zlib bzip2 openssl xz lzo ]
+    ++ stdenv.lib.optionals stdenv.isLinux [ e2fsprogs attr acl ]
+    ++ stdenv.lib.optional xarSupport libxml2;
 
   # Without this, pkgconfig-based dependencies are unhappy
   propagatedBuildInputs = stdenv.lib.optionals stdenv.isLinux [ attr acl ];
 
+  configureFlags = stdenv.lib.optional (!xarSupport) "--without-xml2";
+
   preBuild = if stdenv.isCygwin then ''
     echo "#include <windows.h>" >> config.h
   '' else null;