diff --git a/pkgs/development/libraries/libarchive/default.nix b/pkgs/development/libraries/libarchive/default.nix
index d1917de37d6ac2..3c97ce21ce0702 100644
--- a/pkgs/development/libraries/libarchive/default.nix
+++ b/pkgs/development/libraries/libarchive/default.nix
@@ -2,8 +2,10 @@
   fetchFromGitHub, stdenv, pkgconfig, autoreconfHook,
   acl, attr, bzip2, e2fsprogs, libxml2, lzo, openssl, sharutils, xz, zlib, zstd,
 
-  # Optional but increases closure only negligibly.
-  xarSupport ? true,
+  # Optional but increases closure only negligibly. Also, while libxml2
+  # builds fine on windows, but libarchive has trouble linking windows
+  # things it depends on for some reason.
+  xarSupport ? stdenv.hostPlatform.isUnix,
 }:
 
 assert xarSupport -> libxml2 != null;
@@ -22,7 +24,9 @@ stdenv.mkDerivation rec {
   outputs = [ "out" "lib" "dev" ];
 
   nativeBuildInputs = [ pkgconfig autoreconfHook ];
-  buildInputs = [ sharutils zlib bzip2 openssl xz lzo zstd ]
+  buildInputs =
+    stdenv.lib.optional stdenv.hostPlatform.isUnix sharutils
+    ++ [ zlib bzip2 openssl xz lzo zstd ]
     ++ stdenv.lib.optionals stdenv.isLinux [ e2fsprogs attr acl ]
     ++ stdenv.lib.optional xarSupport libxml2;
 
diff --git a/pkgs/tools/compression/zstd/default.nix b/pkgs/tools/compression/zstd/default.nix
index 8ce434741a5565..c26ca507525fbc 100644
--- a/pkgs/tools/compression/zstd/default.nix
+++ b/pkgs/tools/compression/zstd/default.nix
@@ -18,7 +18,7 @@ stdenv.mkDerivation rec {
 
   nativeBuildInputs = [ cmake ]
    ++ stdenv.lib.optional stdenv.isDarwin fixDarwinDylibNames;
-  buildInputs = [ bash ];
+  buildInputs = stdenv.lib.optional stdenv.hostPlatform.isUnix bash;
 
   patches = [
     ./playtests-darwin.patch
@@ -72,7 +72,9 @@ stdenv.mkDerivation rec {
       --replace "zstdcat" "$bin/bin/zstdcat"
   '';
 
-  outputs = [ "bin" "dev" "man" "out" ];
+  outputs = [ "bin" "dev" ]
+    ++ stdenv.lib.optional stdenv.hostPlatform.isUnix "man"
+    ++ [ "out" ];
 
   meta = with stdenv.lib; {
     description = "Zstandard real-time compression algorithm";