diff --git a/pkgs/tools/misc/mktorrent/default.nix b/pkgs/tools/misc/mktorrent/default.nix
index b2f7fdf2a90..c88f12c74d1 100644
--- a/pkgs/tools/misc/mktorrent/default.nix
+++ b/pkgs/tools/misc/mktorrent/default.nix
@@ -11,13 +11,11 @@ stdenv.mkDerivation rec {
     sha256 = "17pdc5mandl739f8q26n5is8ga56s83aqcrwhlnnplbxwx2inidr";
   };
 
-  makeFlags = "USE_PTHREADS=1 USE_OPENSSL=1 USE_LONG_OPTIONS=1"
-    + stdenv.lib.optionalString stdenv.isi686 " USE_LARGE_FILES=1"
-    + stdenv.lib.optionalString stdenv.isLinux "CFLAGS=-lgcc_s";
+  makeFlags = [ "USE_PTHREADS=1" "USE_OPENSSL=1" "USE_LONG_OPTIONS=1" ]
+    ++ stdenv.lib.optional stdenv.isi686 "USE_LARGE_FILES=1"
+    ++ stdenv.lib.optional stdenv.isLinux "CFLAGS=-lgcc_s";
 
-  preInstall = ''
-    installFlags=PREFIX=$out
-  '';
+  installFlags = [ "PREFIX=${placeholder "out"}" ];
 
   buildInputs = [ openssl ];