diff --git a/pkgs/development/tools/misc/autoconf/default.nix b/pkgs/development/tools/misc/autoconf/default.nix
index b4c3d371529..bd31a688278 100644
--- a/pkgs/development/tools/misc/autoconf/default.nix
+++ b/pkgs/development/tools/misc/autoconf/default.nix
@@ -10,7 +10,7 @@ stdenv.mkDerivation rec {
 
   buildInputs = [m4 perl lzma];
   
-  unpackCmd="lzma -d < $src | tar -x ";
+  unpackCmd = "lzma -d < $src | tar -x ";
 
   doCheck = true;