diff --git a/pkgs/development/compilers/gambit/build.nix b/pkgs/development/compilers/gambit/build.nix
index e06c05b1f244..9481078fd941 100644
--- a/pkgs/development/compilers/gambit/build.nix
+++ b/pkgs/development/compilers/gambit/build.nix
@@ -1,5 +1,5 @@
 { gccStdenv, lib, git, openssl, autoconf, pkgs, makeStaticLibraries, gcc, coreutils, gnused, gnugrep,
-  src, version, git-version,
+  src, version, git-version, stampYmd ? 0, stampHms ? 0,
   gambit-support, optimizationSetting ? "-O1", gambit-params ? pkgs.gambit-support.stable-params }:
 
 # Note that according to a benchmark run by Marc Feeley on May 2018,
@@ -26,6 +26,7 @@ gccStdenv.mkDerivation rec {
   bootstrap = gambit-support.gambit-bootstrap;
 
   nativeBuildInputs = [ git autoconf ];
+
   # TODO: if/when we can get all the library packages we depend on to have static versions,
   # we could use something like (makeStaticLibraries openssl) to enable creation
   # of statically linked binaries by gsc.
@@ -61,9 +62,9 @@ gccStdenv.mkDerivation rec {
     # "--enable-coverage"
     # "--enable-inline-jumps"
     # "--enable-char-size=1" # default is 4
-  ] ++
-    # due not enable poll on darwin due to https://github.com/gambit/gambit/issues/498
-    lib.optional (!gccStdenv.isDarwin) "--enable-poll";
+  ] ++ gambit-params.extraOptions
+    # Do not enable poll on darwin due to https://github.com/gambit/gambit/issues/498
+    ++ lib.optional (!gccStdenv.isDarwin) "--enable-poll";
 
   configurePhase = ''
     export CC=${gccStdenv.cc}/bin/${gccStdenv.cc.targetPrefix}gcc \
@@ -74,19 +75,22 @@ gccStdenv.mkDerivation rec {
            XMKMF=${coreutils}/bin/false
     unset CFLAGS LDFLAGS LIBS CPPFLAGS CXXFLAGS
 
-    ${gambit-params.fix-stamp git-version}
+    ${gambit-params.fixStamp git-version stampYmd stampHms}
 
     ./configure --prefix=$out/gambit ${builtins.concatStringsSep " " configureFlags}
 
     # OS-specific paths are hardcoded in ./configure
     substituteInPlace config.status \
-      --replace "/usr/local/opt/openssl@1.1" "${lib.getLib openssl}" \
-      --replace "/usr/local/opt/openssl" "${lib.getLib openssl}"
+      ${lib.optionalString (gccStdenv.isDarwin && !gambit-params.stable)
+         ''--replace "/usr/local/opt/openssl@1.1" "${lib.getLib openssl}"''} \
+        --replace "/usr/local/opt/openssl" "${lib.getLib openssl}"
 
     ./config.status
   '';
 
   buildPhase = ''
+    # The MAKEFLAGS setting is a workaround for https://github.com/gambit/gambit/issues/833
+    export MAKEFLAGS="--output-sync=recurse"
     echo "Make bootstrap compiler, from release bootstrap"
     mkdir -p boot
     cp -rp ${bootstrap}/gambit/. boot/.
diff --git a/pkgs/development/compilers/gambit/gambit-support.nix b/pkgs/development/compilers/gambit/gambit-support.nix
index 13827b4a59c7..f78c99a50700 100644
--- a/pkgs/development/compilers/gambit/gambit-support.nix
+++ b/pkgs/development/compilers/gambit/gambit-support.nix
@@ -13,7 +13,7 @@ rec {
         --replace "$(grep '^PACKAGE_VERSION=.*$' configure)" 'PACKAGE_VERSION="v${git-version}"' \
         --replace "$(grep '^PACKAGE_STRING=.*$' configure)" 'PACKAGE_STRING="Gambit v${git-version}"' ;
       substituteInPlace include/makefile.in \
-                --replace "echo > stamp.h;" "(echo '#define ___STAMP_VERSION \"${git-version}\"'; echo '#define ___STAMP_YMD ${toString stampYmd}'; echo '#define ___STAMP_HMS ${toString stampHms}';) > stamp.h;";
+        --replace "echo > stamp.h;" "(echo '#define ___STAMP_VERSION \"${git-version}\"'; echo '#define ___STAMP_YMD ${toString stampYmd}'; echo '#define ___STAMP_HMS ${toString stampHms}';) > stamp.h;";
     '';
     modules = true;
     extraOptions = [];
@@ -28,13 +28,13 @@ rec {
 
   gambit-bootstrap = import ./bootstrap.nix ( pkgs );
 
-  meta = {
+  meta = with lib; {
     description = "Optimizing Scheme to C compiler";
     homepage    = "http://gambitscheme.org";
-    license     = lib.licenses.lgpl21; # dual, also asl20
-    # NB regarding platforms: continuously tested on Linux,
-    # tested on macOS once in a while, *should* work everywhere.
-    platforms   = lib.platforms.unix;
-    maintainers = with lib.maintainers; [ thoughtpolice raskin fare ];
+    license     = licenses.lgpl21Only; # dual, also asl20
+    # NB regarding platforms: continuously tested on Linux x86_64 and regularly tested on macOS x86_64.
+    # *should* work everywhere.
+    platforms   = platforms.unix;
+    maintainers = with maintainers; [ thoughtpolice raskin fare ];
   };
 }
diff --git a/pkgs/development/compilers/gambit/unstable.nix b/pkgs/development/compilers/gambit/unstable.nix
index a689991a1e13..26761d67d35d 100644
--- a/pkgs/development/compilers/gambit/unstable.nix
+++ b/pkgs/development/compilers/gambit/unstable.nix
@@ -1,13 +1,15 @@
 { callPackage, fetchFromGitHub, gambit-support }:
 
 callPackage ./build.nix {
-  version = "unstable-2020-09-20";
-  git-version = "4.9.3-1234-g6acd87df";
+  version = "unstable-2023-07-30";
+  git-version = "4.9.5-3-ge059fffd";
+  stampYmd = 20230730;
+  stampHms = 151945;
   src = fetchFromGitHub {
-    owner = "feeley";
+    owner = "gambit";
     repo = "gambit";
-    rev = "6acd87dfa95bfca33082a431e72f023345dc07ee";
-    sha256 = "0a3dy4ij8hzlp3sjam4b6dp6yvyz5d7g2x784qm3gp89fi2ck56r";
+    rev = "e059fffdfbd91e27c350ff2ebd671adefadd5212";
+    sha256 = "0q7hdfchl6lw53xawmmjvhyjdmqxjdsnzjqv9vpkl2qa4vyir5fs";
   };
   gambit-params = gambit-support.unstable-params;
 }