diff --git a/pkgs/by-name/gn/gnu-smalltalk/package.nix b/pkgs/by-name/gn/gnu-smalltalk/package.nix
index 89df07a91afc..7ca522465f7f 100644
--- a/pkgs/by-name/gn/gnu-smalltalk/package.nix
+++ b/pkgs/by-name/gn/gnu-smalltalk/package.nix
@@ -33,14 +33,13 @@ let
   });
 
 in
-stdenv.mkDerivation rec {
-
-  version = "3.2.5";
+stdenv.mkDerivation (finalAttrs: {
   pname = "gnu-smalltalk";
+  version = "3.2.5";
 
   src = fetchurl {
-    url = "mirror://gnu/smalltalk/smalltalk-${version}.tar.xz";
-    sha256 = "1k2ssrapfzhngc7bg1zrnd9n2vyxp9c9m70byvsma6wapbvib6l1";
+    url = "mirror://gnu/smalltalk/smalltalk-${finalAttrs.version}.tar.xz";
+    hash = "sha256-gZoV97qKG1X19gucmli63W9hU7P5h7cOexZ+d1XWWsw=";
   };
 
   patches = [
@@ -50,6 +49,8 @@ stdenv.mkDerivation rec {
     ./0001-fix-compilation.patch
   ];
 
+  enableParallelBuilding = true;
+
   # The dependencies and their justification are explained at
   # http://smalltalk.gnu.org/download
   nativeBuildInputs = [ pkg-config ];
@@ -72,13 +73,13 @@ stdenv.mkDerivation rec {
 
   hardeningDisable = [ "format" ];
 
-  installFlags = lib.optional emacsSupport "lispdir=$(out)/share/emacs/site-lisp";
+  installFlags = lib.optional emacsSupport "lispdir=${placeholder "$out"}/share/emacs/site-lisp";
 
   # For some reason the tests fail if executated with nix-build, but pass if
   # executed within nix-shell --pure.
   doCheck = false;
 
-  meta = with lib; {
+  meta = {
     description = "Free implementation of the Smalltalk-80 language";
     longDescription = ''
       GNU Smalltalk is a free implementation of the Smalltalk-80 language. It
@@ -87,11 +88,11 @@ stdenv.mkDerivation rec {
       language, well-versed to scripting tasks.
     '';
     homepage = "http://smalltalk.gnu.org/";
-    license = with licenses; [
+    license = with lib.licenses; [
       gpl2
       lgpl2
     ];
-    platforms = platforms.linux;
-    maintainers = with maintainers; [ ];
+    platforms = lib.platforms.linux;
+    maintainers = with lib.maintainers; [ ];
   };
-}
+})