diff --git a/pkgs/by-name/gn/gnu-smalltalk/0001-fix-compilation.patch b/pkgs/by-name/gn/gnu-smalltalk/0001-fix-compilation.patch
new file mode 100644
index 000000000000..1784942f3ed0
--- /dev/null
+++ b/pkgs/by-name/gn/gnu-smalltalk/0001-fix-compilation.patch
@@ -0,0 +1,26 @@
+diff --git a/packages/iconv/iconv.c b/packages/iconv/iconv.c
+index ba2c38a7..55c2e737 100644
+--- a/packages/iconv/iconv.c
++++ b/packages/iconv/iconv.c
+@@ -66,7 +66,7 @@ iconvWrapper (iconv_t handle, OOP readBufferOOP, int readPos,
+              int readCount, OOP writeBufferOOP, int writeCount,
+              OOP bytesLeftOOP)
+ {
+-  const char *inbuf;
++  char *inbuf;
+   size_t inbytesleft;
+   char *outbuf;
+   size_t outbytesleft;
+diff --git a/packages/xml/expat/expat.c b/packages/xml/expat/expat.c
+index 0ceee46c..4ea35289 100644
+--- a/packages/xml/expat/expat.c
++++ b/packages/xml/expat/expat.c
+@@ -573,7 +573,7 @@ gst_XML_ParserCreate (OOP parserOOP)
+   XML_SetNotationDeclHandler (p, gst_NotationDeclHandler);
+   XML_SetStartNamespaceDeclHandler (p, gst_StartNamespaceDeclHandler);
+   XML_SetEndNamespaceDeclHandler (p, gst_EndNamespaceDeclHandler);
+-  XML_SetSkippedEntityHandler (p, gst_SkippedEntityHandler);
++  XML_SetSkippedEntityHandler (p, (void (*)(void *, const XML_Char *, int))(gst_SkippedEntityHandler));
+   XML_SetReturnNSTriplet (p, true);
+ 
+   if (!saxEventSequenceClass)
diff --git a/pkgs/by-name/gn/gnu-smalltalk/package.nix b/pkgs/by-name/gn/gnu-smalltalk/package.nix
index 07d83d8bdd13..7ca522465f7f 100644
--- a/pkgs/by-name/gn/gnu-smalltalk/package.nix
+++ b/pkgs/by-name/gn/gnu-smalltalk/package.nix
@@ -33,22 +33,24 @@ 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 = [
     # The awk script incorrectly parsed `glib/glib.h` and was trying to find `glib/gwin32.h`,
     # that isn't included since we're building only for linux.
     ./0000-fix_mkorder.patch
+    ./0001-fix-compilation.patch
   ];
 
+  enableParallelBuilding = true;
+
   # The dependencies and their justification are explained at
   # http://smalltalk.gnu.org/download
   nativeBuildInputs = [ pkg-config ];
@@ -71,13 +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
@@ -86,11 +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; [ ];
   };
-}
+})